£745 is a little steep, I'm also 23 and my insurance is £500 with only 1 year NCB, do you have any NCB's?
I'm with Direct Line, ring them up and do a bit of bartering, I recon they'll be able to beat £745 and you're a girly! Most insurers love girls, and you might be able to get the excess down a bit too.
The most concerning thing imo is the price, £4500 is too much for an 03 147. Even if it's got all the belts changed recently and is full leather etc with all the trimmings I wouldn't pay that much. 2 years ago I bought my 147 Lusso for £3000 belts changed full leather, 18" brand new Italian Antera rims.
I think you could get something very very good, probably as good if you hunted for £1500 less! But deffo get an Alfa, they're the best way to go! Good luck