Yes, you can switch to washerhelp.com if you want. But Ammon's advice no longer applies. The situation has changed and you need to do it a different way. Quite a bit different, in fact. That's essentially what everyone in this thread has been trying to tell you.
Thanks again for your time Ron. Maybe that's the problem, I haven't ever said I want to change focus to washerhelp.com. I only ever said that I want to change where the physical pages are, and if you are right when you said it doesn't matter where the pages physically are, then that's the exact reassurance I always wanted :-)
I want to keep focus on .co.uk which (with Ammon's help) Google has long known is the real site. It's just that I'm moving hosts and now have the ability to host the pages at either the .com or the .co.uk domain.
I don't want to mirror the current situation where all pages are hosted at washerhelp.com because although that's how I started my site, I changed focuss 4 years ago to washerhelp.co.uk and all significant IBL's and Googlebot goes to .co.uk so it's logical to me that the site should now be uploaded to washerhelp.co.uk.