I'd go for an S2 with limited mods.

Running big power will mean more things to go wrong and less useable.

Have a decent alarm on the thing as they are so easy to knick and get one that is rot free as possible and mechanically good over mint condition, as it is bound to pick up stone chips, dents and scratches in everyday use.

Look to companies like need2insure (ask for Paul) as they do classic policies so you could insure it fully comp for as little as £200 a year.