New house needs utilities companies connected - any experience here?

[Lioninthesun]

Builder has just asked which electricity company I will be using and I want to get opinions and advice; are there any special offers for first connections? I don't really know how to go about it as usually they would want to charge from connection, wouldn't they? Hoping the house is about 3/4 months off completion but don't want to end up paying 2 lots of bills for all utilities! Any advice?