I've decided these are a good idea, and I'd like to fit one. The trouble is
that the only suitable products I've found using google are from US
companies, designed for 110V. Does anyone know of a UK supplier for this
sort of thing?

[For anyone who doesn't know what I'm on about, a whole house fan is a
fairly powerful fan that vents hot air from the house into the attic space
(and thence outside), and draws cool air in through open windows etc. The
idea is that you run it when the house is too hot, and the outside
temperature is significantly cooler - typically to cool things down at night
after a very hot day.]