My house is two and a half years old. When I bought it I spoke with the builder about fixing the wall bracket for a 14" TV to a partition stud wall, non-load bearing, non-exterior and definitely no breeze block, just a cavity! I was told that heavy duty cavity fixing would do the job. I was somewhat scpetical of this as there is considerable torque on a wall bracket holding up a 14" CRT, so I went round to one of the houses that were still being built and spoke to the plasterer. He said the same thing! He told me that the walls were stronger than they looked but cavity fixings would be OK.
I gingerly did what I had been told, after all the house was new, if I had a problem I could get the builder to sort it out. Well, after two and a half years the TV is still there. I used the same fixings for the wall bracket for a 37" Panasonic plasma in the master bedroom and the whole thing is rock solid.
One word of caution. Plaster skimmed walls are NOT drylined walls. Skimmed walls will only ever be as good as the material behind them. Proper stud walling, delicate and brittle though it may appear, seems to be perfect for the job.