Gerrardasnails:Whatever you do, don't pay a specialist av installer to do a job that someone with DIY skills (not me!) or a local builder could do in an hour.
Hmmm, sounds like good advice until you realise there could possibly be a bit more to it. I'm not saying don't follow Gerrards' advice, I'm just saying consult an AV specialist as well and see what they say. Absolutely, I'm sure a proper genuine builder will get you the bracket you want attached to the wall, but will they have any knowledge of other things you should think of before you get this done? Not likely.
Just my opinion as always.