Latest is West Tuning with its rather awkwardly named Cooper S 240 Thruxton. Chances are you won't have heard of the firm, which works out of impressive facilities adjacent to - you've guessed it - Thruxton circuit. Supercharger conversions and remapping German metal have been its speciality for 18 years, so when the Cooper S appeared, the route was obvious. And the end result is the Electric Blue 'S' pictured here, complete with uprated engine, modified suspension, larger brakes, bigger wheels and some subtle aesthetic tweaks.

Let's look at the engine first. The extra ponies have been liberated by concentrating on solid efficiency improvements, rather than just winding up the boost and hoping for the best. To that end, the throttle body is machined to enlarge it by 20 per cent and careful attention to the cylinder head ports and combustion chambers, along with substantially larger exhaust valves, also yield significant flow gains.

These valves are worked via a high-lift camshaft, the exact specification of which West is keeping close to its chest. From here, burnt gasses now exit via a tubular exhaust manifold, which feeds into a less dense sports catalyst, and ultimately a discreet, but tuneful, Milltek stainless steel exhaust system.

In tried and tested style, a smaller, faster spinning supercharger pulley raises the boost levels on the Eaton blower, while West's own in-house remapping system (which leaves the dealer-diagnostic information untouched) tweaks ignition timing, fuelling and the rev-limiter to suit the new requirements. An emissions-compliant 244bhp is the end result, with a serious 207lb ft of torque. Sounds interesting.
So does the chassis. Up front, geometry tweaks aim to improve traction, sharpen turn-in and reduce understeer, while Koni dampers and Eibach springs lower the car 25mm to help add further poise to the baby BMW. And just look at the brakes. Huge Brembo four-pot callipers, clamping 330mm discs that should last many a serious trackday session without fading. More importantly, they just slot behind 17in alloys, but in this case West Tuning has opted for an eye-catching set of 7.5 x 18in BMW X5-esque rims. Combine those with a BMW 'aero' bodykit, some restrained colour-coding, plus a lick of silver paint on the roof, and it's clear that West Tuning knows how to spec-up a demo car.

Twist the ignition key and there's a mellow, deeper tone to the exhaust as the supercharged unit sparks up, settling into a refined, smooth tickover. Any suspicions that the high-lift camshaft trades performance for a lumpy, unrefined idle are quickly dispelled, even when starting from cold. Now the big test. Into first gear, move off and subject the engine to a high- gear, part-throttle, low-rev ordeal before the coolant's warm.

Happily there's no hint of misbehaviour here, not a snatch, judder or any other gremlin that you might expect from a tuned motor. So it's time to move on to explore the extra mid-range urgency, the primary benefit of the conversion's additional torque.

Hang on beyond 4500rpm and there's real potency, the West S howling - motorcycle-style - all the way to the 7250rpm limiter. It's a vividly exciting ride as you dispatch the gear ratios in the Getrag 'box at a frenetic pace, accompanied by a delicious cacophony of supercharger whine and sharp exhaust note. The performance is pretty staggering the first time you try it, all the way from rest to three-figure speeds.
Here's a MINI that could embarrass an Impreza or two.

More impressively, you can allay any fears of it being a torque-steering, uncouth, dynamic disappointment. Granted, the DSC light flashes in the first three gears, but even with the system switched off, a mixture of dry and damp B-road tarmac sees the feel-packed steering remain well-behaved, wriggling only slightly through your palms as the torrent of grunt is unleashed through the 18in rubber. Turn-in seems keener, while the well-poised, adjustable chassis balance remains. Combine this with the hugely powerful, negative-G-inducing brakes, and this modified Mini punches well above its weight.

Downsides? Cost. As tested, you're looking at ΂£5664 including fitting and VAT. Of course, there's always the option for the financially challenged of a piecemeal approach to the upgrades. Go the whole hog, though, and the result is probably the quickest Cooper S we've yet driven and one of the easiest to live with. Even a standard Cooper S delivers a grin-factor that even traditional sports cars struggle to match, and with all this extra firepower the effect is intensified.