Electricity supply to new extension

mr_green_3

Hi All,
I have almost completed a two bedroom etc extension to my house and am wondering what is the cheapest way of having electric installed.I could possibly just connect into the house supply but it may be that if we could rent out the extension then it would be better to have its own supply and meter. Do you have to use Central networks contractors, Energy Services or are there other ways of doing it. The existing main supply is right next to the extension. Has anyone had any idea of costs etc. Energy services have sent be a six page application form to fill in for them to cost it out, but having dealt with them previously when I wanted the electricity pole removed I am just a bit wary of them. Any suggestions would be appreciated