I have gone with Ovo.
First Utility:
Average phone call till someone answers is approx 30min (20-40min) Ive done it 6 times now!
They have not communicated ANYTHING in 48 days. Basically I signed up, they said I would get a welcome letter with change over date etc....
After 2 weeks I ring saying I have no letter, they said I was being impatient and I had to give 28 days (Oki fair enough). After 35 days I ring them back saying still nothing. All they would tell me is yes they would be taking over my supply but couldn't tell me when and my account number. Great what use is any of that to me? 46 days later ring again and get no more information then before.
Rang Energy Omburdsman, they said it was quite normal for them, you probably wont ever here from them! I took their advice and rang First Utility who were actually very good (once I got through) and said yes its their mistake, we are sorry, we will cancel your contract and discharge you. Which basically means I can go with whoever I want.
So they were Oki in resolving it, however took ages on the phone (Which isnt 0800 like Ovo) and generally useless and couldn't tell me anything on the other 5 attempts when I rang! As you can imagine I have very little faith with First Utility now so have gone with Ovo.