Just a quickie based on my own recent experience. When I was with npower standard I asked if I could switch to cheaper online. No and company advice was leave us and then come back. With this experience even smartbum me arrived at Scottish Power on Online Energy Saver 4 assuming I would have to look out for myself SP - SP. At some point I said you've got this extra accreditation don't you at least have to tell me what's best for me SP - SP? A GOOD CS person agreed rather shamefacedly that, that should be the way on the 'spirit of the law' but it wasn't. She then said in your case if you go into your account you can switch whenever you like. Sure enough there were all the attractive choices there and I should have explored BUT foolishly and forget the extra accreditation I assumed that they would have explained what you can do online clearly. Southern Electricity don't make it clear before joining they say you can only bill online, actually you can do more by e mail within the online account.
I'll be schtum now.