Is it just a case of pushing really hard or do i need some suction cups to pull it out?

Any help would be greatly appreciated :-D

If it's anything like my mk3, pushing with your feet is enough as I found out when someone in the back of my car thought it was a good idea to do it...

Depends - If you're doing a van conversion, the easiest way it to stanley knife the seals out. If you're planning on reusing them, you can either chance it and boot it out (sometimes works, sometimes they break), or run the proper tool/a few old screwdrivers round the rubber and prise the glass out, though this can be a practised art.

push the rubber seal over the lip from inside...take your time

Just push it out with your feet from the inside laying down on the back seat. Go to the edges of the glass all the way round to start easing it. Dont be afraid to give it a good push, I've never had one smash on me yet doing it this way and I've done a few now.