Not all facelifts are 225s, do a search for engine codes and you will find a full write up, as mentioned you may get a high miler for the budget you have, however dont let this put you off, also see if you can get one with good service history.
Get the cambelt done every 50k, thats what the majority of S3 owners have and recommend, i just had mine done as did a few others on here, again if you do a search you will find quite a few threads on cambelt changes.
I had mine done with the waterpump and fanbelt all for £270 inclusive.
Where about are you based??
Also for a car, look in the usual places, soz if im telling you to suck eggs, but not alot of people check all these places....
autotrader
pistonheads
exchange and mart
Cheers
Nilz