That's a pain Miss-Taken :o(
Could it be your aerial? Or how about the aerial cable? We kept getting a dodgy reception only to find that the wire in the aerial cable had come loose (under the sealed plastic) so the connection wasn't as good leading to poor reception.
Unless anyone else comes up with better suggestions of why you may have lost the channels, it might be a good idea to buy a booster box for a stronger signal (unless you already have one of course lol), see if that helps.
Sorry I can't be of much help Miss, but I know how annoying it is to have the channels but not be able to view them!