I'm with BT now, before that I was with sky for years.
BT's 24/7 support may seem good but it's truly terrible. Most of the time you'll end up with a call centre in India where BT have clearly skimped on the cost - they're considerably worse than other call centres in India.
I've resorted to forum based tickets which take days to respond, and even then one ticket was resolved quickly and the other took ages.
On the other hand, BT's router is much better.
Ashington (Northumberland) Exchange