Had the same problem with sound breaking up on my G4 box during Man City match. Tried changing from surround sound to stereo and issue still there. But if I switched channel the problem disappeard for a short time. It could be happening on other HD channels but on Saturaday I spend most of my time on BT Sport.
Dave123 - do you have an Onkyo A/V receiver? If so, see this post:
It appears there is an intermittent compatibility issue between the Humax YouView STB and Onkyo receivers. A simple workaround is to use an S/PDIF optical cable if you have a spare S/PDIF input on your receiver (they are assignable on most Onkyo A/V receivers).
I now seem to have this problem. Every 60 seconds I get a slight pause in sound. Tried playing with sound options does not seem to make any difference. BT have done a good job competing with SKY but they really need to sort these technical issues out. I suffered for months with 416 channel freeze issue, I now have this problem as well as random box freezes, never mind the performance of the box in responding to handset commands.
Of course I could report it to the helpdesk but will then be forced to go through the 50 step reset process until I get to some one who has a clue what they are talking about, mind you last time I got a new hub out of it :-).