Rear light cluster

Wasn't sure where to post, I have a mk2 2003 scenic. I wanted to remove the rear light cluster to change a bulb but the torx bolts were dethreader. I thought I'd buy a new cluster break the old one out and turn the bolts using a pair of mole grips. Problem is they are very rusty and stuck, I'm not entirely sure what they screw into behind, how do I get them out and if I remove the boot lining can I get to
The rear of the bolts, what do I need to get to put new bolts in andsomething first to attach to behind and how do I get them out? Cut them out?

Rear light cluster