I had one of these for 4 years, although it was a younger model when I bought it. I had about 40k miles with minimal service costs an tyres and that was it. Then I blew a turbo just as I planned to sell it and really should have trusted the job to a specialist at about £2500 but made some mistakes in my judgement. Anyway, the point is that even with all the costs of fixing the turbos etc, I only spent about £4000 total in 4 years of ownership and depreciation was another £6k. At circa £5k, you'll have barely any depreciation - if anything they will go probably start to go up in value as the numbers reduce. I sold mine for just under £5k.
Also, I used to get around 24Mpg after my remap, and that was with LOTS of enjoyment of the remap..
On a long run, and if I felt like it, I could nudge 30Mpg, so they really arent that bad.
There are some expensive failures waiting in the wings in these cars, but if you can get your hands dirty, most of it can be tackled yourself, and spares are plentiful, sadly at sub £5k, many cars are being broken as they make more in parts than whole. Over on AudiSRS there's been two cars recently sub £2500 and they were by no means dogs, just high mileage. One was broken IIRC at 300k miles (yes!!). The engines are VERY strong if serviced reasonably, its the other bits that mount up.
However, IMHO you cant get as much of a strong, quiet, sleeper car with over 270Bhp for the money that gives so many smiles!
I would watch out for turbos (buy a forum car over an autotrader one anyday), recent service at a decent garage or specialist, and, especially, a PROPER cambelt change - it should have all belts, all tensioners, thermostat and other ancilliaries done (bill around £500-£750)
There's some great cars out there, with all the care lavished, and I really wouldnt be put off by over 100k miles, at least the car will have been used properly; mine was circa 80k when it went, and whilst I REALLY looked after it, you could tell it had done lots of journeys, rather than miles. I've seen examples with twice my mileage in better overall trim condition. Not many as shiny though
Hope this helps!