Thanks for the info.

Whilst waiting for a reply on this I have been doing a bit of digging and a few people have mentioned using the 'Transport Tool', within the resource pack, to move accounts from one BES to another. Is this approach do-able? Or shall I look at a total DB move to avoid losing other config?

I am thinking that I will move the BESX DB first, then install a new BESX and then tackle exchange afterwards.