A clutch would never be covered by any warranty as it is a "wear and tear" item. At £1400 I assume it was the clutch and dual mass flywheel which were replaced, not uncommon on modern diesels.

I would snap their hand off at £225 for the drive shaft damper.

You've probably been more unlucky than average, but VWs are not always the tough reliable cars people think they are.

Very unlikely to get any warranty cover on a 3 year old vehicles clutch, thats just one of those things. i'm afraid, they probably fitted a new DMF at the same time, hence the price, whether that was really needed you'll never know.

What i would suggest is you find a VW specialist (preferably) or one of those rare excellent most make indies, your part of the world probably has a few, and get them to look after your cars from now on, the sort of place who strips your brakes cleans and lubes them on a full service because thats what should happen.

Regarding the present driveshaft damper, it's probably as good as you're going to get the offer of some goodwill to fix it, and i'd be inclined to let them do that (assuming that £225 is the whole job complete incl labour, not just the parts) then wash my hands of them.

The dealership were going to do the usual trick of throwing a complete driveshaft on instead of fixing what was wrong (why not throw the car away instead, thats the natural next stage), then probably saw the look on your face and decided that they'd maybe raided your piggy bank enough for this year, i'd let them do this one job and then never give them another penny of my hard earned.

Understand your disgust fully.

My mate who used to work in a big south london VW dealership told me he has seen clutches burn out on cars with 6k on them.