If looked after these cars will last - there is a guy on one of the various VAG forums who has clocked up something like 180k on his 1.8T IIRC.
As for servicing, once the bushes and cambelt/waterpump jobs are out of the way its fairly cheap to maintain;
Tyres - usual prices etc, but obviously depends what wheels, profile etc,
Oil & Filter - £35 from the dealers for the parts - about a 30min job on the drive. I do mine every 5k which some may call excessive but that's "how i roll" lol,
Clutch - not actually sure when these tend to go, but your looking at a minimum of £500 to replace. Re-mapped cars will genrally require the clutch doing sooner although this is more aimed at the derv's as their torque figures screw the ballgame up.
And thats about all i can think of for now!
Oh, and i'd deffo invest in a cheapo dummy VAGCOM cable and the freeware version of the software off ebay (~£13 delivered) just so you can scan for your own fault codes as these cars rely on fault codes for 99% of things and if you have a problem the first thing anyone will say is "get your codes scanned".
Also - MAF sensors and coilpacks WILL fail at some point - both of which will result in lumpy idle or a misfire but are cheap as chips to fix

£35 per coilpack (but make sure if one goes to replace all 4) or about £90 for a MAF. As with any parts DO NOT buy non VAG OEM, the cheaper aftermarket stuff is just that - cheap and sh!t.
Hope this helps you out mate.