There's plenty to choose from for £5000 I'd say anything under 100k miles would be worth looking at. Remember Low mileage cars could need all the small common bits doing.
Why is the 100k mileage figure an issue here?
Always buy on condition, spec and history - in no particular order! Not an arbitrary mileage figure
I am still confused by this apparent hangup people have on a mileage figure?
Mine has done 172k on an 08 plate and is in perfect order - no advisories on the last two mot's and is tight as a drum
It will see me over the 200k mark I am sure - if anything was going to break by now apart from consumables it would have!
As for potential purchasers
Check condition of the vehicle - yep they do rust in areas others have said, also look for accident damage and shoddy repairs. A/C should be icy cold and dont be fobbed off with "it only needs a recharge"
Get them to recharge it and try again - can be VERY expensive to repair if the compressor has failed. If someone is running a performance vehicle on ditchfinder tyres that cost pence per corner instead of Goodyears/Pirelli or other performance car tyres I wouldnt imagine that vehicle has been looked after. Dirty/Stained/Ripped seating - why isnt it immaculate for sale? Not been cared for
DSG or manual boxes have their own issues - ensure DSG oil changes have been carried out, Mechatronic units in the DSG box can cost upwards of £1500 to replace and if its a manual check the clutch as others have said. New clutch/flywheel and release bearing is around £1k fitted. Cambelts need doing every 4 years or 40k miles and around £350 to carry out including a new water pump.
Know your spec and what you want - check for Highline Dash clusters, Multifunction Steering wheel controls, Cruse Control,Folding mirrors, BiXenon Lights, SatNav headunits, 18'' Monza Wheels, 2 x working keys, Leather seats - the list goes on and although the majority can be retrofitted it wont be cheap.
Service history - Stamps in a book are NOT service history, good enthusiast owners keep EVERY receipt for the vehicle. I do! Make sure you carry out an online MOT history check - verify's mileage and you can often spot a dodgy MOT, ie a fail with a long long list of issues on a Monday then a pass a couple of days later at a different garage with not a single advisory and no paperwork or receipts to back up the repairs!
Good luck and happy car shopping - pm me if you need any further advice