If sheer performance numbers are what you're after, I think you'll struggle to find a quicker insurable first car than a 205 XS. Thanks to a close ratio gearbox, twin choke carb and advantage of having all the weight (and structural integrity) of a empty crisp packet, it will embarrass some much more powerful machinery whlist not costing too much to insure.
Engine wise mine has had a euro spec Rallye Cam fitted, a 4 - 2 -1 Manifold and a rebuilt carb. The engine result is a car that feels pretty damn rapid (and this is coming from someone who has regular access to a V8 BMW). Granted it isn't going to destroy every car you'll stumble upon in the Traffic Light grand prix, but it's more than quick enough to put a smile on your face when you need it to.
Mine might be available if you're interested? It's a 10th of what you were considering spending, still has a classic appeal and you'll be able to get insured on it, in your name, 100% legit.
Other than that, I'd back the idea of thinking outside the box and going for bigger engined cars. A 2.5l Subaru Legacy is only £80 more expensive to insure than my 1360cc 205

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LUL WUT

What kinda
door knob would do that?
Someone who was pure, diluted WIN
