All freeview channels except BBC channels suddenly vanished what could be the cause?

A week or two back i found i wasn't able to watch anything but BBC channels so i retuned my TV and it only found BBC channels nothing else i've done a few manual retunes and it's found some of channels i had apart from some rare occasions where a channel has worked for a bit i always get "service not running" or at best "no signal" what could be the cause of this freeview was working just fine a couple of weeks back