Back on-line now...
Many apologies for the service interruption over the last two days. The hosting company was subject to a Distributed Denial of Service attack, which brought the server down, then ran into hardware trouble before restoring all the files from an off-site back-up.
The good news is that ultimately this all proved successful. I am not happy with the service level, though, in that it should have been possible to get the site up and running from a different server while they rebuilt it. More than 48 hours off-line is not good at all.
These are details that should make no difference to your life whatsoever. I am as yet undecided as to whether I need to seek alternative hosting services (balancing up my dissatisfaction with recent events and the unknown risks of leaping from frying pan to fire). But I'm really hoping I won't have to write a post like this again any time soon.