Dunno about the sky box but the firestick should, in theory, work from a specific USB on the TV - it is usually marked which port supplies power. I mean, all USB ports can supply power but I think these ones are set up to supply extra (or something like that). From experience I know it's a bit of a hit and miss which devices will work and which still need plugged in. I've yet to get a firestick to work without also being plugged in but, in theory, it can (and Amazon say it can).