Hey folks!
so... update to this. I visited the gentleman on this forum and cut out the replacement window successfully, it was a pain in the ** but it came out after some blood sweat and tears, it then sat in my shed for a few months.
the rain this past few weeks has shown me that this is an issue that needs fixing, i had a pool of water on the load cover the other morning that you could do your washing up in. so i bit the bullet and called an auto glass company in leeds area called autoglaziers. top people can vouch for them.
guy came out and had a look at the replacement window i had and said he could fit it no problem, turns out they're not easy to get hold of at all, the girl who i spoke to on the phone couldnt find one from any of her suppliers so was relieved when i said i had a replacement window already. So if anyone is breaking an XC70 P2, don't scrap it before you cut out the rear side windows as trust me someone will want them at some point!
anyway guy came around and removed the old window by... levering it a little! it came straight out and when it came out it was evident that it was only being held in by silicone! not even proper window glue! so its clearly been accidentally broken and replaced as cheap as possible to sell the car on. The guy said he was surprised it hadn't fallen out when i closed the doors or worse whilst driving. lucky!
he then removed the silicone and the old glue that was still on there, and primed it with some stuff to stop any rust
then a bit of new glue (proper stuff) and she was sorted
£40 for the job and i'm a happy boy. So now i need to find out the paint code, get the trim sanded, primed and painted.