In theory the backup I made using Synk onto my firewire disk should allow me to plug the external disk into my Mac (or any recent Mac?) and have it boot up off that disk, making my work environment exactly as it was at the moment of the backup. I tried something similar the last time my PC crashed but that never worked properly and I ended up having to copy things across and re-install applications.
I found a colleague with a Mac today and tried my backup – my heart in my mouth – and it seems to work just as advertised! (At least on the basis of a few minutes clicking around).
So there will be a week of chaos while my machine is being repaired after which I should be able to go back to an almost completely normal life (technologically speaking). Thank you Apple and Synk!