You don't need a >£10k 300hp car to have fun driving. I would suggest a two car solution. Focus bore-box or similar to placate her, and something cheap, old and fast to keep you entertained.
Your Vectra is worth what? 10k? Release that capital, buy 3k family car, and £1500 fun car. Then hide anything you spend on your fun car so as to avoid this situation again.
Possible cheap fun cars
Alfa 75 V6
Alfa 155
Carlton GSi 3000
Mk2 Golf GTI
Mk2 MR2
Your Vectra is worth what? 10k? Release that capital, buy 3k family car, and £1500 fun car. Then hide anything you spend on your fun car so as to avoid this situation again.
Possible cheap fun cars
Alfa 75 V6
Alfa 155
Carlton GSi 3000
Mk2 Golf GTI
Mk2 MR2