Thanks Graham. I actually have a trade account with Farnell, so that
shouldn't be a problem (we always need other things at work!).

If you can humour me for a moment though - if the PSU was designed for
110V (and I will remember to use the trasnformer this time...), is it
not a 110V or thereabouts Varistor that I want? I've ben studying a
Varistor selection guide and it seems as though you should select a
comonent that is rated slightly higher than the intended voltage,
however other terms (Clamp voltage for example), I don't understand.

I was actually browsing the RS site looking at these :

ERZV07D241 metal oxide varistor,150Vrms

am I way off?