Here's my tuppence worth!
Retaining a single community is the right way to go.
However, it is likely that us UK guys will 'group' together as a matter of course under topics that we readily identify with and require resolutions to, advice about etc etc.
UK is different to USA
ie we are stuck with 4 non-bank affiliated payment gateway offerers. All the others are banks which are so tied up in beaurocracy it is unbelievable! It takes a mountain of paperwork and visits to the bank to apply for a Merchant ID. Then it takes weeks for the sodding banks to refuse you!!!
In USA you are fortunate to have such a variety who want your business and are fast in setting you up. Hours or even minutes.
Are we envious? YOU BET YOUR SWEET BIPPY we are!
Only problem for us if we choose a US based gateway like 2checkout, PayPal etc is the currency issue.
So, there is my 2p worth. I think a UK forum might work going forward, but for now, keep it altogether - like a family.
By the way, this is a fantastic site.