I use ADSL. Not cheap from them - 30 quid for half a meg - but the servers are bloody good and I get a bit of web space as well. Surely you are on ADSL by now?
And anyway, you don;t need to use Clara for broadband etc to use them for mail.
When I was on ISDN, I used them for mail reception on my domains and used DEMON to get to them. Outgoing mail had to go via demon of course, but I can access my claranet mailboxes from anywhere in the world via any ISP.
Thats excellent. I transfered mine the same way to Clara anyway..and for simplicity changed the hosting rather than the indirection to hem. Its a simple matter of getting the ISPTAG changed and then the new provider can edit the master files themselves.
Moving your domain and mail first and keeping the same ISP for the actual transport stuff is the easy way to go.