It was an accident! The remote.mydomain.co.uk self signed cert in SBS2008 expired today, and I went through the process of renewing by going through the wizard in the SBS console. I've not done this for some time, so when it asked for my domain, I stupidly entered remote.mydomain.co.uk which in turn ended up with SBS configuring both the cert and Exchange for the domain of remote.remote.mydomain.co.uk.
I re-ran the Internet Connection Wizard, then re-ran the "Set up your Internet Address" wizard and this time entered just mydomain.co.uk
The problem now is that Exchange has NOT re-configured itself for mydomain.co.uk and is now not accepting emails. I ran the Fix My Network wizard, but I get an error:-
The server cannot connect to the SMTP connectors. Ensure that Exchange is running, then try again