This just at certain times of the day? Don't use Sky Go that often myself but can give it a blast tonight if people think there may be a problem somewhere?
For me, I've tried 3 times over the last week or so and it's always been between 7pm and 11pm.
I'll give it a go tonight in which case although my connection is pretty rapid so not sure if I'll be able to replicate. Least I can do is make sure the traffic classification etc. is correct.