I'm not sure why you'd be able to watch after going to Sky Sports... however, all the BBC channels recently switched broadcast satellites to Astra 2D (the same as ITV) this satellite has a much narrower focus area... your dish alignment needs to be spot on for the Astra 2D channels to work correctly.
Get hold of a local specialist from
here and get the dish looked at. They will also be able to tell you if you have an LNB problem (possible as it has to respond to a 22kHz tone from the digibox to receive 2D) or if it's the digibox itself at fault.
Good luck
edit: Look at
this page a little way down you'll see an article "Channels missing after fitting Quad LNB?"
Although the answer is meant for Sky+ users who have just had a heavier quad LNB fitted, you can use the same test to see what your "2D" reception is like

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