Drop in a 1600 16v out of the polo gti, nice and easy 125bhp straight off and revvy. Goes straight in and can use a 085 gearbox. Put throttle bodies on it!

Perhaps sum complete 40mm Jenvey ones for £400?

Run on megasquirt, nice and cheap and heady power. That or carbs, alot of rally cars run 1600 16v on carbs, revs the nuts off them, sounds awesome!
GT engines (3F) can easily get them from Sandburn Auto's in Coventry.