Don't mean to sound smug but I have a Victorian 3 bed house with high ceilings and draughty sash Windows. I've managed to run the house (electricity and gas) for just under £500 this year with flow energy and am now due a whopping rebate. I had an email from mse cheap energy club and switched last year. Really glad I did. The customer service has been amazing too .
Please note I don't work for the company, I'm just super impressed I've found such a reasonable fuel company.