Video only picking up 2 stations - why?!

I retuned my TV when I bought an aerial booster. I then connected up the video and reset the channels on that too. But it is only picking up TV3 and CH4 (I don't have satellite). I have tried manual installation but nothing works.
Any ideas why and what I can do?

Did the video previously pick up more than 2 channels, or is this the first time you've tuned it in?
Did you buy the video in the North or the UK?

Sounds like a uk video to me

Or the signal booster is boosting some signals and filtering others. The OP does not say what channels being received on TV and if it's also connected to the booster.