I had exactly the same problem when I migrated from Claranet to Sky (which I subsequently dumped because they were technically inept) and then Demon. Neither could help because; Sky are not in the hosting game and you need to be hosted by Demon and I did not want to move. In my case, the domain mane was becoming valueles so I dropped it; if this is not so for you, you may need to move to Talktalk (if they have a hosting facility, or, to someone else if they don't. Have you considered using PlusNet as your ISP? Don't know how good they are, but at least you'll solving your email problem.