Hi Darren,
I would try one of the following
1 If wall is a false / stud wall, cut out plaster board isin the desired location adapt stud work i.e. make a frame for the new opening and recover studs creating a gap, fixing to new location ??? possible to use a stand to stand screen in new gap??
2 if wall is real /brick, find out if it is a supporting / load bearing wall, if so seek proper advice, if not cut out gap add lentle and place in screen??
3 if real wall and you dont want the fuss and mess of cutting out gap, build up a false /stud wall in front of real wall, leaving gap for screen and allowing a soild fixing onto real wall. this will give the appearanc eof a flush screen and may allow you to sink in (the same way) the speakers for the screen?
Sorry descriptions are not very good but hopefully you get the jist?
Cheers