Mini Mark III and onwards ( 1970–2000 )

The Mark III Mini had a modified bodyshell with enough alterations to see the factory code change from ADO15 to ADO20 (which it shared with the Clubman). The most obvious changes were larger doors with concealed hinges. Customer demand led to the sliding windows being replaced with winding windows—although some Australian-manufactured Mark I Minis had adopted this feature in 1965 (with opening quarterlight windows). The suspension reverted from Hydrolastic to rubber cones as a cost-saving measure. (The 1275 GT and Clubman would retain the hydrolastic system until June 1971 when they, too, switched to the rubber cone suspension of the original Minis.)

Production at the Cowley plant was ended, and the simple name Mini completely replaced the separate Austin and Morris brands.

In the late 1970s, Innocenti introduced the Innocenti 90 and 120, Bertone-designed hatchbacks based on the Mini platform. Bertone also created a Mini Cooper equivalent, christened the Innocenti De Tomaso, that sported a 1275 cc engine similar to the MG Metro engine but with a 11 stud head, a special inlet manifold and uset the A clutch instead of the verto type. The most important feature was the utilization of homocinetic shafts, avoiding the rubber couplings.

By this stage, the Mini was still hugely popular in Britain, but it was looking increasingly outdated in the face of newer and more practical rivals including the Ford Fiesta, Vauxhall Chevette, Chrysler Sunbeam, Volkswagen Polo and Renault 5. Since the late 1960s, plans had been in place for a newer and more practical supermini to replace it, though the Mini was still the only car of this size built by British Leyland for the home market.

Reports of the Mini's imminent demise surfaced again in 1980 with the launch of the Austin Mini-Metro (badging with the word mini in all lowercase). In New Zealand in 1981, the Mini starred in a road trip movie directed by Geoff Murphy called Goodbye Pork Pie. The Mini was beginning to fall out of favour in many export markets, with the South African, Australian, and New Zealand markets all stopping production around this time.

Although the Mini continued after the Metro's launch, production volumes were reduced as British Leyland and successor combine Rover Group concentrated on the Metro as its key supermini. Indeed, 1981 was the Mini's last year in the top ten of Britain's top selling cars, as it came ninth and the Metro was fifth.

* Mark III (introduced in November 1969) had wind up windows with internal door hinges except for the van and pickup models. The boot lid lost the original hinged number plate and its recess shape and a large rear colour coded lamp was fitted in its place, along with larger rear side windows.

* Mark IV (introduced in 1976) had a front rubber mounted subframe with single tower bolts and the rear frame had some larger bushes introduced. Twin stalk indicators were introduced with larger foot pedals. From 1977 onwards, the rear indicator lamps had the reverse lights incorporated in them.
* Mark V (from 1984): all cars had 8.4-inch (210 mm) brake discs and plastic wheel arches (mini special arches) but retained the same Mark IV body shell shape.
* Mark VI (from 1990): the engine mounting points were moved forward to take 1275 cc power units, and includes the HIF carb version, plus the single point fuel injected car which came out in 1991. The 998 cc power units were discontinued. Internal bonnet release were fitted from 1992.
* Mark VII was the final twin point injection with front mounted radiator.

Mini Clubman and 1275GT ( 1969–1980 )

In 1969, under the ownership of British Leyland, the Mini was given a facelift by stylist Roy Haynes, who had previously worked for Ford. The restyled version was called the Mini Clubman, and has a squarer frontal look, using the same indicator/sidelight assembly as the Austin Maxi. The Mini Clubman was intended to replace the upmarket Riley and Wolseley versions. A new model, dubbed the 1275GT, was slated as the replacement for the 998 cc Mini Cooper (the 1275 cc Mini Cooper S continued alongside the 1275GT for two years until 1971). The Clubman Estate took over where the Countryman and Traveller left off.

Production of the Clubman and 1275GT got off to a slow start because the cars incorporated "lots of production changes" including the relocation of tooling from the manufacturer's Cowley plant to the Longbridge plant: very few cars were handed over to customers before the early months of 1970.

Early domestic market Clubmans were still delivered on cross-ply tyres despite the fact that by 1970 radials had become the norm for the car's mainstream competitors By 1973 new Minis were, by default, being shipped with radial tyres, though cross-plies could be specified by special order, giving British buyers a price saving of £8.

The 1275GT is often incorrectly described as the "Mini Clubman 1275GT". The official name was always just the "Mini 1275GT", and it was a separate, distinct model from the Clubman (albeit, it shared the same frontal treatment as the Mini Clubman, and was launched at the same time).

In 1971, the 1275 cc Mini Cooper S was discontinued in the UK, leaving the Mini 1275GT as the only sporting Mini on sale for the rest of the decade. Innocenti in Italy, however, continued making their own version of the Mini Cooper for some time, and In Australia from mid 1971 to the end of 1972, the Clubman GT was locally produced. This was essentially a Cooper S in Clubman body, equipped with the same 7.5-inch (190 mm) disc brakes, twin fuel tanks, and twin-carb Cooper S 1275 cc engine. While the UK built 1275GT was not nearly as quick as a 1275 Mini Cooper S, it was cheaper to buy, run, and insure. It was the first Mini to be equipped with a tachometer. It also featured a standard-fit close-ratio gearbox. Performance of the 1275GT was lively for the time, achieving 0–60 mph (97 km/h) in 12.9 seconds, and the excellent midrange torque offered a 30–50 mph (48–80 km/h) time in top gear of only nine seconds. The bluff front, however, meant that the model struggled to reach 90 mph (140 km/h). The 1275 cc A-series engine could be cheaply and easily tuned, though the cheap purchase price and prominent "sidewinder" door stripes meant that this model developed a reputation as something of a "boy-racer special" during the 1970s and into the 1980s.

The Mini Clubman and 1275GT were responsible for two motoring "firsts": they were the first vehicles to use a flexi printed-circuit board behind the dash instruments (universal nowadays, but technically advanced for 1969). Secondly, the 1275GT was the first vehicle to be offered with run-flat tyres; from 1974 this model could be ordered with optional Dunlop Denovo tyres on 12-inch (300 mm) diameter rims. In the event of a puncture, the Dunlop Denovo tyre would not burst and quickly deflate, but could continue to be used safely at speeds of up to 50 mph (80 km/h). This was a useful safety feature, although the increased road noise and relatively poor grip of this tyre meant that many 1275GT buyers ignored this option.

Throughout the 1970s, British Leyland continued to produce the classic 1959 "round-front" design, alongside the newer Clubman and 1275GT models. On the Australian market however, all Minis (including the commercial derivatives) gained the Clubman front. Clubman sedans were marketed in Australia under the Morris Mini Clubman name when introduced in August 1971, and as the Leyland Mini from February 1973.

The long-nose Clubman and 1275GT offered better crash safety, were better equipped, and had vastly better under-bonnet access, but they were more expensive and aerodynamically inferior to the original 1959 design. The Mini Clubman and 1275GT were replaced in 1980 by the new hatchback Austin Metro, while production of the original "round-front" mini design continued for another 20 years. At the end of Clubman and 1275GT production, 275,583 Clubman saloons, 197,606 Clubman Estates and 110,673 1275GTs had been made.