I feel your pain
I ran my GTI with a slipping clutch for about 10 months, it only gets worse.
If yours is a K03 GTI you could replace with OEM clutch and it should be fine for 12-18months, maybe more before it starts slipping again. There have been lots of folk on here having problems with Sachs clutches, they are also quite expensive
-Helix are available from Awesome GTI and will be fine for your level of power, not heard any bad things bout these (I would have got one if these if I'd have kept my GTI)
- southbend do good replacement clutches also, have to google them though as there aren't many suppliers.
Don't bother with a single mass flywheel, as it will only knock at idle and pulling away. The Dual mass is there to protect your gear box from the torque of the engine. If your DMF isn't making any noise, I'd just leave the old one in as OEM replacements are about £330
Hope that helps