You can get a good road worthy mk2 RS2000 for 8-9k, some are more, some are less, mexicos are harder to value IMO, seem to be a lot rarer these days, there arer also 1600 sports which also fetch good money, and the daddy, the RS1800, approx £45k if you can find one.

An RS1800 for you, personaly, I'd love a goldcrest
One of them^^ Rare as rocking horse shit these days!!