I know that you mods don't like quidco only deals posted so I'll put this MMRN.
Quidco currently have 3 energy suppliers offering £60 for dual switch (BG, Scot power and Pow Gen). One was actually cheapest for me and other two not too far behind. So what Ive been doing for the past few months is switching between all three. I have been waiting for payment but I suppose you could switch when payment is validated. At the moment I'm switching every 2 months and the cash back means I'm only paying half my energy costs.