thanks for the reply paul, the rack i have is the equinox avi ts which has a built in plasma stand. it has 2 brackets which attach to the back of the tv, no problems there. they then hook onto the wall mounting bracket which is attached to a vertical arm on the rack rather then on the wall. it's the wall bracket part of it that is too narrow.
the shop i got it from contacted atacama who say i need a different part which should be here soon but i'm not convinced as the shop said atacama weren't aware it wouldn't fit. although the 2 brackets/hangers are big enough to reach the holes on the back of the tv, none of the supplied screws are anywhere near big enough to use. also when i took the circular covers off the tv it looks as though the part i will screw into is made of plastic. it doesn't say anything in my tv's manual about it and now am wondering if its supposed to be wall mounted? i know the 42 inch can be but not sure about the 37 now, mainly based on the weak looking screw holes and atacama not knowing what would be suitable on what seems quite a popular tv.