On 4th-sept the internet connection to our uk servers failed, causing our uk worlds to become temporarily unavailable.
I phoned the company that provides the hosting & bandwidth for the uk servers, and was told that the problem was causing by their main router failing. In fact apparently not only had their main router broken, but the backup router had broken also! The situation was further exasperated by the air-conditioning to one of the racks failing, causing equipment to overheat. All this meant it took longer than expected to get everything fixed.
The hosting company managed to get the uk servers back online earlier today (5th sept), by swapping in a 3rd replacement router, but it seems the replacement was unable to handle all the traffic so the servers were somewhat laggy.
Apparantly the original router has now been fixed, so they've all been moved back to that one. It seems everything is finally working, the servers are online and there doesn't seem to be any lag (fingers crossed!)