I eventually contacted trading standards and a solicitor and was advised to put everything in writing and give them one last chance to fix the car before rejecting it. So that's what I did. It has now been with the supplying dealer for over a week, and this is their summary:
They have acknowledged the misfire and managed to reproduce it. They have done all of the tests which VW asked them to perform, and all came back negative (as in no fault found).
HOWEVER... VW have apparently acknowledged this problem with the R line cars (Golf R, Scircocco R, Audi S3) and think that it may be a fuel starvation issue. Their solution for ME, is to never let the car dip below quarter of a tank of fuel if I'm going to drive it hard!!!
Does everyone agree that that is wholly unacceptable??? Surely that's just ME driving around the problem!? Has anyone else had any similar issues with mis-firing? Do any of you drive your car hard on less than quarter of a tank and if so, have you ever had any problems?
It would also help me if you could let me know what fuel you normally put it as I have pretty much been advised to use V Power only (I usually use Tesco super (99).
I would greatly appreciate anyone's advice / opinions on this as the whole experience has turned into a nightmare so far

Thanks
Lee