I would echo Terry's sage advice and make sure that your TV flylead is up to scratch as this is about the only item in the equation which you can do much about. It sounds very likely from your description that you are suffering from impulse interference where bursts of radio frequency energy are emitted all across the frequency spectrum from switch or relay contacts opening or closing in domestic electrical equipment or road vehicles outside.
For the same reason, you should keep your mobile phone away from your integrated digital TV (idTV). Also keep your computer well away from the idTV as both the processor and the monitor screen generate a lot of RF.
The sort of TV flylead you purchase for a pound or so at B&Q is complete rubbish, one step up from wet string. What is absolutely essential for the very low signal strength digital terrestrial television (DTT) signals is a high quality double screened coax flylead. This has a copper foil screen and a tightly wound copper braid around that. The cheap flyleads just have a thinly wound copper braid and no foil screen and let all manner of external interference in. They are only OK for the analogue signals, which are transmitted at immense power. Currys and Canterbury Hi Fi flog decent flyleads for a tenner up.
A booster would almost certainly be of no use whatsover. The place for a booster is up near the aerial to compensate for losses in a long coax run to the TV. Plugging one in at the TV end just amplifies the attenuated signal together with all the rubbish picked up on the coax run and makes matters worse.
You should also definitely have the idTV plugged into a surge protector/mains filter, not directly into the mains socket. This will help to eliminate mains borne interference.
Doubt if inversion effect is the culprit. This is actually not from other DTT transmissions but from analogue transmissions received outside their normal range due to being refracted by abnormal atmospheric conditions. Impulse interference is far more likely to be the reason.
Will have more to say on this at a later date but am off to bed (sound like Vic!).
Induction interference and mobile phone interference:
http://www.ukfree.tv/fullstory.php?storyid=1107051300&PGSTART=100
Inversion effect:
http://www.ukfree.tv/helpme.php?faqid=1107051114
Dover TV mast at Church Hougham:
http://tx.mb21.co.uk/gallery/dover.php