Hi Durbinator and welcome to the GTI forum. This is my go-to place for info, so enjoy.
I'm in Bristol too, just bought my car about 4 weeks ago (I paid £4,700 privately - see my other posts for pics and spec) and am really happy with it. I came from a Porsche Boxster S (we had a baby!), and although it will never corner like a Porsche it is an awesome car in many ways, and certainly more practical... I'm gradually updating some stuff, so here's my opinion FWIW:
£6.5k will get you a good car. Early cars are good, but be aware there were some revisions around 07. Check if it's a 1K or 5K chassis - there were some improvements, some not so good changes, but I'm not an expert here. It mainly affects you when looking for parts.
I wouldn't be troubled too much by mileage, although I would personally stick below 100k. A badly driven, town car is often much more prone to problems than a well-driven motorway car. Get an inspection and a HPI check done, buy with full history and V5 present, check all the receipts, check MOTs for recurring problems and ask loads of questions - when they last changed the oil (if you're going DSG check DSG oil change too), discs and pads wear (and brand), tyre wear, usual stuff.
Specific mechanical issues seem to be cambelt as you mentioned, as well as the DV valve and Cam Follower, but these 2 are relatively cheap and easy to fix. If they've added a PCV Breather, or Blank (sometimes called Delete) kit then so much the better. Obviously usual checks - oil leaks, gasket leaks etc. always worth doing. Ask them to take the engine cover off so you can see if there are leaks on the head gasket etc.
Electrical - notorious are windows etc., but check all electrics esp. door buttons like mirrors etc. Make sure you get radio reception as the cables can go.
Bodywork - wheel arches notorious, so check under there for rust, as well as bottom of doors. Of course, Monza alloys get whiteworm corrosion, so either accept it and budget approx. £300 to fix, or buy a car with recently refurbed wheels. Check boot handle for corrosion too, and exhaust.
Mods - personally I would be happy looking at an already modded car as often they are looked after better than other cars, as the owner is always tinkering, but usual rules apply - if it looks like carbage it probably is, and if they don't know what they're talking about when you ask about the mods then think twice. If they look like they might do doughnuts all day long then walk away... a sports car is meant to be driven hard, just not badly. Common mods include uprated turbo, air intake, intercooler, big brake kits, coilover suspension, poly bushes, anti-roll bar, LSD etc. A quick search on here will tell you everything you need to know.
Spec - if I had my chance again I would defo look for Xenon headlights, highline clocks, multi-functional steering wheel (MFSW), cruise control and centre armrest as they can be a bitch to retrofit (mine has centre armrest and cruise already but point remains the same!). Make sure Xenons were factory-fitted and if not, make sure they are the real deal with self-levelling and ballasts etc. If you're going DSG, make sure you get flappy paddles too. Other popular spec includes sunroof and reversing sensors, although I don't like the look of them, and go for an RNS510 ("top of the range") or RNS310 (slightly quicker interface) stereo - RNS means sat nav, but if you weren't bothered by that you can get RCD500. If you get an RNS you will probably need a new CAN Gateway (look it up). MFD2 and RCD300 to be avoided. Having said all that, I'm about to put a Kenwood head- unit in mine! I don't like to have an extra bluetooth box on the dash. If you go DAB you can get an aerial that hides in the boot pillar. Worth looking at. Puddle light heated folding door mirrors would be ideal. 18" Monza alloys for the look, 17" for the ride (although most people say it doesn't make that much difference), heated leather for me, but also like the cloth GTI seats - if you are looking at pictures online, the heated seats buttons are in between the climate control dials - if there is a blank there, they are not heated.
Have a look at this car on Ebay - item number 181559134165 - it's probably got every bit of spec you could hope for, so is a good start if you want to learn about those sorts of things. Personally I would travel for the right car - this might not be your choice, but gives you a great idea of spec and is actually good value.
Let me know if you want to come and look at my car - happy to show you around! Today I will mostly attempting the DV replacement... Otherwise, keep looking on here and hope you get what you want.
