Picture problems with a Phillips tv

[Sad Mum]

Hello, we have a Phillips 28PW6515/05 tv that has always worked well until a couple of weeks ago and it is now getting rapidly worse.
First we just noticed red and green vertical bands of colour with a faint ghost of writing (from another chanel?) in the back ground. Now the picture is almost unwatchable with big blocks of red and green and bands. You can see a ghost from other digital channels well enough to read them now and areas of single colours especially white have wiggly lines that look like map contour lines in them. It's just as bad on terrestrial or cable. and now sometimes the picture breaks up altogether with white staticy looking lines for a few seconds. The picture when you can see is grainy. It seems slightly better when it warms up...though at first it seemed better when cold. It can suddenly be ok for an hour of two at random too.
It happens on all inputs rf scart and video and audio inputs whether all plugged in or only one at a time.
Sound is fine.
We can't afford a new tv or even to get this one repaired. My husband is a service engineer (not for tvs) and good at electrical stuff. There are no loose connections and he's resoldered a couple of joints that looked black like there was a bad connection but it hasn't helped.
All suggestions very gratefully recieved.
Thanks