OK, after the mild disaster that was Pipex's hosting service I've got another potential provider on-line.
Rather than just switch over and then have the pain of some bits (mostly this rather old forum) going super slow I've got it mounted on another URL for testing.
Please check out http://www.choctest.fast2host.com/ it's a straight copy of the site and database. Anything you do in there will be overwritten once I re-copy the live site (assuming it performs ok). Let me know if you find any speed issues in there (particularly with reading and posting to the forum).
If it all goes ok then I'll recopy the database and switch the addresses around - if not, then I guess I'll move to the next hosting provider on my list.
Thanks for all your help.