Thanks for the replies.
KMR... at £1750 definitely falls into the "would want to try one properly before splashing the cash" bracket.
Buckmark - don't see many advertised, but a good friend who has one (also has a GSG as well as proper target Pardinis) suggested the Buckmark would be the best option. He said of his GSG that it was surprisingly accurate , but awful sights and trigger took away any pretension of being a target pistol. Unfortunately he lives 500 miles away, so I can't go and look at his toys.

All the reviews I have read on forums and so on suggests the Colt Gold Cup Trophy (Walther) is more accurate that the GSG, and with effort the trigger can be made to be quite good (but no where near proper target pistol territory).

I am more than happy to do some smithing myself to try to improve the trigger, but if the gun cannot hold a two inch group at 25m, then it isn't for me.

At £600, the colt might be my best option, and if it didn't work out, maybe reach for a KMR then. But if a Buckmark was available at the right time/place ....

Problem I have is no where to go and try them. Hopefully get my variation back in a couple of weeks, but no point in rushing things before then.