Set a spec in your head of `must haves`and stick with it.
For me it was:
-Sprint/Black/Ibis
-BOSE
-FBMFW
-Armrest
But it came with, flappy mirrors, auto lights/wipers, cruise, sunroof etc...so they were a bonus.
Forget NAV (RNSE), you can retro that later just make sure you budget £600ish or it.
If its got it then great, if it hasnt then dont let it put you off.
Check Autotrader and Pistonheads EVERY day religiously.
Be prepared to travel.
I did a 500mile round trip for mine and it had only been on PH Classifieds literally for a few Hrs.
Took me a while to find a lightly used one in spec I wanted but I saved around £4K on a used 5month old car.
Mid 20s MPG is easy to achieve even without driving too gentle and some heavy traffic thrown in (this is what achieve with this mix.)
30mpg is easy on run, even when pushing on a bit.
Im a big Golf fan, in particular the MK5, its a great car but having 2 of them before my S3, the S3 just feels more special in everyway.
But it is alot more money than a Golf so it should be.
IMO, the looks, cabin finish, and all weather access to the power (in particular with a remap) are major plus points.
Whether you think that bit extra is worth it is another thing.
Probably still worth driving them back to back, and then make your own choice.
Certainly dont discount the Golf, its good, buts its not an S3.
Neither are bomb proof, legendary German build quality is a bit of a myth these days, but they do have a nice `feel` of quality, even though stuff will break and wear out earlier than they should.
Mine is 2yr old 20K miles and the cabin is pretty much as new with the obvious exception of a few crease in the hide where its had to support 15st for the last 20month. The hide wears better on the std S3 sets than the Golf hide seats.
REVO is a no brainer.
It is brilliant, do it straight away whether it be s Golf or S3.
Hope this helps.
Good luck.
Cheers
Paul