I recently bought a Mk5 Golf GTI and I am restoring it to "as new" as much as possible while keeping it near stock.
Engine wise the service history is immaculate with a service every year except one. It has only done 38,000 miles so must be one of the lowest in the country. For me, and this may not be popular on here, I think a iconic car (which the Mk5 is) shouldn't be messed with much and deserves hanging onto.
The car was a bit of a state as it has sat for a while and was used to take kids to school. The result was the interior trim was badly damaged in places (back to the white plastic), bits were missing (ashtray insert, bottle opener) and lots of nail marks were on stuff like the handles. (Handle rubber bit is £15 btw)
The interior has now been refurbed including the seats and I'm now working on the outside, including replacing the passenger window because it has a scratch on the inside! Wheels were okay but had white worm so those are being done and I need a couple of new tyres as the old ones were cracking (michelin Pilot 4).
I've altered a couple of things - stereo is now a pioneer DAB203 with apple carplay and the rear boot struts are being replaced for Skoda auto opening ones. But in general just about everything except the floor mats are OEM (and these will likely be changed).
Next job is new brakes pads and discs (brembo but stock spec), rear springs (corroded) and while it is up on the ramps everything will get a good clean and screws resprayed. The cam follower, refurb steering wheel and a bit of respray and it should be done. In total it will have cost me a fair bit (all in £9,000) but for that I will have a car that will either sell at the top of the market or will last me years.
Planning on doing a readers cars thing over xmas when I have the time.
Not many stock Mk5 GTIs out there and even the ones that are need work so for me preserving one is the right thing to do.