Your mistake was to enter the sony shop, its just a few bits of metal stuck together. I got a decent folding arm tv mount for the GFs house, cost me £9 delivered on amazon. It holds the tv on the wall, and it moves where I want it, no idea what a £50 one can offer over this as its behind the TV and never seen. Amazon are great for this stuff, better than ebay usually as they are a bit stricter with sellers, but not always. Avoid a company called Designer Habitat at all costs though, they just cancel stuff and take ages to refund.
This is why the high street is really dying, people sick of being ripped off. 20 years ago you'd only have expensive TV retailers to buy from, I call it the
Monster Cable Effect. I worked with a guy that swore blind he could see the difference in picture from his PS3 to his TV because of the new cable he had, when I couldn't see a thing. Maybe my eyes are crap, but just maybe he was convincing himself the £50 he just spent wasn't wasted.