Hi welshtraveller,
It's a couple of years since I was last in Sveti Konstantin when it was in full swing (been 3 or 4 times since but out of season, when the resort is effectively closed).
I can't recall having seen bars with Sky there (I would have avoided them like the plague anyway, as I hate football), but it's quite likely that most hotels will have the games on, as most Bulgarians that I know love their football. I'd suggest checking with hotel reception/tour operator rep on your arrival - I'm sure that they will point you in the right direction.
Golden Sands has a couple of places boasting live Sky TV in my old Balkan Holidays leaflet - The Sky Bar on the top floor of Hotel Sirena and the Taj Mahal Indian restaurant. There will, doubtlessly, be many more places showing the matches, as there will in Varna but they are likely to be easier to find in Sveti Konstantin or Golden Sands..
Baldur