If you need a new DMF and clutch, both LUK and Sachs make one. The Sachs one is much more expensive, that's not to say it's better (as the OEM one is LUK), but it may be. I don't know but to could be worth asking round.
As for going single mass, don't do it. Some don't work well and shake the van to bits (there's someone on here that went single, hated it then paid again to change back) and some do.
VW designed it for a DMF, why change. If you go single, unless you drive like a nun, you are going to put additional strain not he gearbox, exactly what VW were trying to avoid when they went for a DMF.
Sure there have ben successful DMF to SMF conversions, but ask yourself do you want to risk it and potentially wreck your box.
Hope it's not as your looking at £700 - £1000 for a replacement (all inclusive). Heard a couple of cheaper quoted though.
Fingers crossed for ya.