Soldato
This thread becomes especially relevant for me now, as I will be taking the keys to my first flat tomorrow and will need to choose new suppliers.
I stuck with the existing supplier (EDF) for the first year at our new place, because it made the transition easy and I had too much else to worry about (water/phone/broadband/council tax etc etc).
EDF's prices were fair and there were no exit fees.
Remember to take a meter reading the day you get the keys!