Around 2am the server crashed and everything just went offline. By 2.30 Tom the Tech had isolated the problem to the database but what was causing the problem was unclear. He called in a specialist server management firm.
By 6.30 the cause had been identified as an automatic software upgrade and rolling back to the previous version fixed things (lots of other servers went down across the world with the same thing)
We had some corrupted files in the forum system but he sorted that by 7.45am
Unrelated - we are upgrading to a new server shortly. Faster CPUs and 6 instead of 4, double ram, solid state hard drives (about 100 times faster) and a better operating system to run everything. I'm hoping it will be very fast delivering pages.