Regardless of your current electricity provider, the correct point of contact to report a power cut is UK Power Networks:
Online: Report a Power Cut
or
Tel: 0800 316 3105

Ironically, communications providers can be amongst the most difficult companies to speak to if you want to report a fault or outage. Most will try to fob you off with online self-diagnostic tools! Talking to a real human being can be pretty difficult. The following phone numbers may or may not prove helpful if you reach the end of your tether:

BT: 0800 800 151
Sky: 0333 759 1018
Virgin: 0345 454 1111
Talk Talk: 0870 087 8777
Plusnet: 0800 432 0200

Anglian Water's 24/7 leakline number is 0800 771 881

Anglian Water's 24/7 query line is 03457 145 145