The official title of the car is simply Mini-Cooper, but in later years the term Mainstream Cooper would become the generally accepted name of the car to help distingwish it from the RSP Cooper and the later fuel injection model.

The trim level for Rover’s new “top of the range” Mini was somewhat disappointing.

On the outside, the Mainstream was originally available in three colour schemes, Flame Red, British Racing Green Metallic and Black, all with a White Diamond roof. Storm grey Metallic, White Diamond and Quicksilver schemes, all with a black roof, were soon added to the range. Although the car has the familiar “Cooper” contrasting roof, bonnet stripes were omitted from the factory spec.

The bumpers, door handles and boot handle are all chrome plated and the standard "Cooper" chrome finish eight bar grille is used. Rear quaterlights are the opening type with chrome frames.

The Bonnet badge features the words “MINI COOPER” in red surrounded by a stylised laurel wreath in green, all on a circular white background. The badge is finished with chrome wings.

A double pin stripe runs down the side of the car with a laurel wreath decal on the rear quarter panel. This decal is also repeated on the boot lid, positioned above the number plate light which is always painted Satin Black. The twin door mirrors match the roof colour.

The mainstream cars are fitted with the 4.5 x 12 Minilite style alloys similar to the Mini Thirty and RSP Cooper, but the stud holes have been repositioned between the spokes.

Wheel arch extensions are the "Mini Special" type in plain dark grey. Glass is plain untinted.

The interior trim is basic but has potential. The all black colour scheme gives a classic look with a black leather steering wheel, black carpets and black vinyl door cards with a single red stripe. The only thing that really lets it down are the seats. They are all cloth and finished in black “Racing Crayons” fabric. Their basic “flat” design and their "80’s" pattern does nothing for the overall feel of the car. A three-clock binnacle sits behind the steering wheel. Dials include a 110mph Speedo and a tachometer. The green/blue background colour of the instruments is standard on all Coopers.

The central switch panel includes a low brake fluid warning light, heated rear screen switch, hazard warning flasher switch and the main lighting switch. To the left is the choke control and to the right the heater temperature control. The rear fog light switch is in a separate panel to the right of the steering wheel. Lights, wipers and horn are controlled by steering column mounted stalks. A radio cassette player is mounted under the parcel shelf in front of the passenger seat.

The one area that really stands out on the cars is under the bonnet. The 1275cc A-plus engine was developed from the unit fitted to the MG Metro. Controlled by a single HIF44 SU carburettor. With a 10.1:1 compression ratio and a camshaft shared only with the RSP model, it produces a healthy 61 bhp and a top speed of 92 mph. The engines are finished in a red wax treatment with a plain black pressed steel rocker cover. The air box is similar to the one used on the RSP but features a moulded Cooper badge on the intake trunk.

The only real way that the Mainstream engine differs to the RSP is the lack of an oil cooler. All Mini Coopers are fitted with an auxiliary electrical cooling fan inside the left-hand front wing.

The mainstream Cooper was the first production Mini to be fitted with a catalytic converter as standard. A three branch exhaust manifold feeds into a twin-down pipe, which in turn feeds into a single exhaust pipe, which incorporates the catalyst. The back box is a twin silencer design with a sports style tail pipe.

The Coopers share the same dry rubber cone suspension and steering found on all late Minis. The front brakes are 8.4in discs and the rears are 7in drums. The system is split front to rear and is servo assisted.