my e46 M3 was £1400 at 28 with 2 yncb £300 excess
I had a spring go in mine and the tyres on the 19s were £250 ish for the rears
The diff will; have a little backlash in it but not too much, also check the wheels for corrosion on the 19s as theygo real easy with the slightest mark in the clear coat. due to the polished natue not many places will refurb them, cost £450 to get all mine done, and they are never the same as the original finish (although close).
I drove like a nutter most of the time so was getting 14mpg daily but then is had schric cams in it etc (370bhp) so she was uber thirsty, when going for it I used to see 7mpg
If you can afford it then good for you but pleeeeeeeeeeeeeeeeease be careful, I found the e46 far more dangerous than my e36 as it is so softerned up that it fools you into thinking your not going as fast as you are (140mph feels like 80mph) the e36 fed back far more and the lack of ACS+T made you learn the cars limits.
ACS+T in the M will let you drift slightly but it still unbalances the car if your really messing about when it decides enough is enough mid corner (hence why I kept it off and sport mode on)