Thank you so much 'spiderplant', I must be getting clever in my old age! Yes I tried TV direct to box hole on wall and still the same. It's defo not the TV as it lets me watch taped programmes from a freeview box.
As usual Management agencies charge high fees and cannot be bothered. ' oh if it's just yours TV, it will be a fault in you apt, in which case you will be charged' Grrrrr. I am glad you have said its possible we do not all share the same aerial (18 Apts, 3 story high.)
Also such a lot have sky, but I tried my TV in there apt and it worked except for BBC? However it confirms my TV works. Thanks again.