What age / mileage is the car? was £6k a fair price? and are you sure it’s the flywheel? have you got a professional to look at it or are you looking on VAG forums? there’s a lot going on in the general clutch/flywheel/gearbox region so it’d be worth getting your ducks in a row before you throw it back at the dealer with bits of legal jargon you printed off the internet.
Also have you spoken to the warranty company? they’ll have a list of garages they work with. May be daft but have you spoken to VW too? it could be on a recall list and they’re waiting to do it for you.
Come to think of it, have you spoken to the dealer? it’s much better to speak to them direct and say what your issue is politely, safe in the knowledge that you’ve got the SoGA to back you up if he tells you to sod off.