What about a Mini??
One of the "old" ones.
And, in U.K., it shouldn't be dificult to find one for a good price. And parts are also kind of cheap.
It isn't very powerful, but with a few "subtle" mods you can tweak it to 100bhp, that for a car that weights about 650kg.
If you want more, you can tweak it a bit more, with a turbo or something like that and put it around the 140bhp.
If you want even more, there are companies in the UK that make them with Honda Vtec engines, with power around 160-220bhp.
The sky is the limit!
