Still no joy, going to have a long crack at it this weekend with the new seals and mechanism arriving tomorrow for when the inevitable does happen.
For others: if you search youtube for
how to open a VW door ( I can't post links yet sorry) then you'll find some good lock mechanism guides and
how to go in through a door handle, however, you need the lock to be open and I think one of my problems is that it can't be because i've tried going in through the door handle and puling the mechanism but it's not doing anything as if the door is still locked.