Replacing rear window gas struts but stuck attachment

[Flyingpillock]

Merry Xmas all

As a Boxing Day treat I’ve decided to head out and I nstall the new gas struts on my 95 Isuzu mu.
I’m probably the least mechanical minded ill equipped tool wise person I know.
Managed to to get the bolts out at strut pillar attachment point but the point where it attaches to the window just has the whole circular unit in the window spinning with the bolt head on the other side. Tried a g clamp but doesn’t get enough purchase as does a pair of pliers. Any tips

Thanks in advance?

[Flyingpillock]

Turns out walking away for 30mins then returning swearing at it more does the trick!
Thanks anyway, always a great forum for the daily struggle with the mighty mu