Off the top of my head how about a Civic 5dr 1.6i VTEC SE Sport? 136bhp but sane insurance. I just checked
www.parkers.co.uk and they reckon £6k would get you a dealer 2000/X with 40k on the clock. A good private should be about £5k.
I suggest it because it's pretty pokey, reliable, and not overly expensive to run. Also it's not too big. I bought mine because I didn't want big but still needed space for 4 adults with a hatch boot. It's not a Saxo it terms of nimbleness but certainly isn't a sluggard
Is it just and old Rover? It's much better than that!
Sites to help you hunt down the motor of your choice :
www.parkers.co.uk www.honestjohn.co.uk www.autotrader.co.uk
EDIT
OOO a REALLY usefull page I've just found for insurance vs car info:
http://www.motor-car-insurance-uk.co.uk/honda.htm
P.s.
If you can stomach the insurance a Lupo Gti might be small enough