I have an issue with both front windows, they will wind up to within 10-15mm of closing then the winder mechanism starts to slip, can this be repaired? or will i just replace both regulators, i have searched but i cant find replacements 

@Kent80 Seems strange that both of them would have the same issue so I wonder if someone has caused an issue by using a different regulator or bracket, not sure if it's possible to install incorrectly. Do you have a photo with the doorcard off? If it's the correct regulator then the slipping is due to worn 'teeth' on the regulator cable (worm drive).

I expect there are places that sell replacement drive 'cable' or suitable donors from something at a scrapyard then (I haven't ever looked/tried) but I assume you would need to remove the 'bottom-stop' for the window so you can wind the whole worm-drive cable out then put it's bracket onto a replacement drive cable or use a replacement that already has a bracket with the right holes for the channel bracket attached to the glass.

Beetles and Baywindow buses use the same channel bracket but the regulators will be different shapes  due to the door layout so different position of the winder compared to where the regulator 'runner' attaches. That said maybe you could use the worm drive out of one of those which I presume will be readily available via VW Heritage or other as you can buy pretty much every part for them reproduction (unlike Type 86's!).

Mk1 Golf regulators bolt on lower into the door below the lowest position of the window bracket whereas Type 86 bolt on to sheet metal of the door which is roughly where the lowest position of the window bracket is. Depending how different the winder location is maybe Mk1 golf ones could be used and the excess bracket either tucked into the door panel or modified?

Mk2 Polo/Golf went to push/pull cable on pulley type.