Wow, this thread went a bit off track, lol!
At your age a 320i will be fine as it will be more than quick enough and the looks will be more important than how quick it is anyway. Yes the 320i engine has a few known issues so if you can stretch to a 325i it might be better. They'll be the same price to buy and not much more to insure.
My only other question would be, does the smaller engined 320i carry a premium over the bigger engined cars? I'm not really current on 320i coupe prices but I've seen similar spec bigger engined one's for cheaper. £14k just seems like a lot of money to pay for a 320i to me.