@Thomson_adam; I think that if I was considering buying a mk6 GTI with a budget of £10k, most cars fitting your budget are likely to be around 9-10 years old so I’d consider the overall condition and the existence of a comprehensive service and maintenance history more important than specific items of equipment. Also it’s important to check that the timing chain tensioner has been replaced with the latest (third revision) version - have a look at the ‘timing chain failure list’ sticky at the top of the mk6 forum board if you’re not aware of the tensioner issues.
IMO the leather used by VW for the optional leather seats in the mk6 Golf wasn’t very good quality and was very prone to creasing and sagging. That would play havoc with my car OCD
as I don’t like my car seats to have that saggy, lived-in look. I had a mk6 GTD with the standard cloth seats - the same as those fitted as standard in the GTI apart from the colour. I thought they were excellent - some of the best seats in any car I’ve owned. I know the tartan cloth is a bit ‘marmite’, but I really liked them.
Xenon headlamps were an expensive extra cost option on the mk6 GTI; they cost in excess of £1,000 and because of the cost, relatively few cars had them. So you may struggle to find a car with these fitted.
Headlamp bulbs can be upgraded and a reversing camera can be retro-fitted. Bear in mind that if you find a car without a reversing camera and it’s got the standard fit (small screen display) RCD310 radio/CD player, it’ll need to be upgraded to either of the optional RCD510 or RNS510 units. The optional units have the larger screen that’s required for the reversing camera display.
Good luck with your search.