why do I get wavey lines down the sides of the screen top to bottom in waves ? and it turnes itself of after a period of operation

SOUNDS LIKE YOU HAVE A BAD FILTER CAPACITOR IN THE POWER SUPPLY.

With a Thomson its more likely to be the B+ filter but I would have it looked at soon as these things have complex setups and its very easy for a spike to stuff the whole thing up. The usual is mixing Pal and NTSC or dropping all the inputs and the tuner. Also if it does that dont ask for settings because these are local settings, you may be lucky and someone who is local but we "gots to know" where you are if that happens.