Proabbaly time to rethink just how I use this machine. I'm considering dropping it down to a single disk system, but with a much bigger drive. Following a suggestion from jonhoneyball, I'll be running scheduled backups to two firewire drives - and (as ramtops suggests) handing one to a friend when we go on holiday (or sticking it in the car when we're away in the UK).
I have to remember - this PC is my whole livelihood now. And I need to treat it as being that important.
And there are things on it which may not be work, but are still important to me. So I need to back them up as well.