Welcome aboard adavies
I’ve been messing about changing wheels and bits on Golfs for over three decades so have a rough idea of what can and what shouldn’t be done.
VW have been using the same basic wheel dimensions and fitment for Golfs since 2004.
Therefore if you fancy a second hand set of OEM wheels there’s a hell of a lot of choice, and wheels from Sciroccos and Passats will also fit for example (amongst other VW group wheels which share similar dimensions).
There are literally dozens of aftermarket alloy wheel manufacturers, so this could potentially be a very exhaustive search.
In your position I’d be favouring either of the following options.
A set of MAK Wolf alloys which can be specced in a size that takes VW bolts and original centre caps, it’s an OEM inspired design that is manufactured in Italy. They can be bought in singles if you wreck one on a winter pothole.
https://www.senco.es/es/blog/2014/03/noticia-114.htmlOr a set of replica wheels from CM Wheels as referred to above.
Personally I’d go for these
https://cmwheels.com/products/18%e2%80%b3-vw-golf-reifnitz-tcr-style-wheels-satin-gun-metal/ as they’re fairly cheap which will mean you won’t be too upset if one gets wrecked on potholed roads.
The grey colour looks good when clean, hides light brake dust and road salt grime quite well and isn’t diamond cut, thus avoiding discolouration. I’ve run a set for 12 months and just under 8k miles and they’ve held up well with just minimal stonechips to the rear wheels as the only slight blemishes. The downsides are you’ll need eBay centre cap decals and if you wreck one you can’t buy a single wheel to replace it.