Panasonic TX26LMD70 26" Tv

We bought this tv from John Lewis two months ago.Initially we were very pleased with all aspects, but it has developed two intermittent faults. The first is that it emits a continual buzzing noise, which is a real nuisance when watching TV at low volume. The second, more serious fault is that for no apparent reason the colour becomes overlaid with dayglo green and pink, like a bad 1960s pop video. This comes and goes, and has nothing to do with the picture settings. So today the very nice repair men came and took it away (needless to say the faults would not occur in their presence) - so we''ll wait to see if they can rectify the problems. Meanwhile if anyone has any advice on dealing with these faults...