Flip2k3 one of the best things you could do is go on a track day with it. Sounds weird i know but you will b able find the limits of the car and you which you just can't do on the road safely. Should be alot more confident with the car then.

I know where you are coming from though, as i went from a 80bhp 1.4 Clio to a 200bhp Rover Turbo. It is a big step and even bigger f you have just passed your test. Give it a couple of weeks and you will probably want more power again.