Re: Newbie here! I have an A3 but falling for Alfa's!
A mate of mine has a 2 year old A3 2.0tdi, dsg gearbox, s/line interior. I think its a very good car. It goes well, does40+mpg & is very practical & comfy.
The big surprise is that he has had FAR more reliability issues with the A3 than I've had with my Brera over a similar period of ownership. Diesel particulate filter issues, satnav (built in) crashing, & various electrical gremlins. If I had suffered that with the Brera, then everyone would have just shrugged their shoulders & said "well its an Alfa, what do you expect?? But everybody hears of supposed Alfa fragility, yet no one talks about similar problems from supposedly more robust marques.
The big difference is that the Audi dealership he goes to in Cambridge is superb. Really excellent customer service. Nothing is ever too much trouble. They even took him out for a test drive in the R8 whilst his A3 was in being looked at! Alfa dealerships still have much to learn in that respect, I'm afraid.
Also, I don't think the 147 is going to be as quick as the A3, at least if its the same as my mates. I was a bit dissapointed with the one I drove (1.6 petrol brand new), & think his A3 is pretty rapid.
The Alfa range is definitely on the up. The gt,159 & Brera/spider seem to be a MAJOR step up in build quality from certain Alfa's of old, but we still get so much perverse enjoyment out of moaning about alarm niggles & seat mounts loosening that we've got a whole section of the forum dedicated to unreliability!
I don't think Audi forum (if there is one) would allow such moaning!
With your budget of £13k +, I think I'd look at a nearly new 159, GT or Brera, rather than a new 147 which will be superceded soon, which would probably hurt the residual value.
But go for an Alfa, I doubt you'll regret it.