Thanks for that link. This one from their website is quite close to what I have in mind...
http://www.wedi.co.uk/vanity1.htmIt looks a bit like the blue polyurathane insulation I'v had from Sheffield Insulation before - I've used it to build model airplane wings.
I was going to use a vessel type basin with the taps mounted on the vanity unit so I'd have to figure out how to mount the taps without crushing the foam.