It went to their address in Tunbridge Wells; £56.50 for a battery change and pressure test, and they quoted me 5-7 days turnaround. It came back very nicely cleaned as well, in a little Breitling travel case with a cleaning cloth protecting it. No idea where it was sent back from though, so I don't know if it was serviced at Tunbridge Wells or if it was moved on from there.
They did tell me about some local suppliers who would send the watch back to Breitling for me, but I thought it easier to cut out the middleman. The closest watchmakers who could actually do a service themselves were a couple of hundred miles away.
I was very happy with the service, to be honest.