Many thanks to all who have responded to me on this thread - there have been
some excellent suggestions (and words of advice).

I've arranged cancellation of the order from ColdSeal - though not through
their head office number, whose 'cancellation line' is permanently busy
(why am I surprised?) but via a local office.

As a result I've got out of the contract but it's cost me both the deposit
and the 'insurance'. Unfortunate - yes. But next time I'll read the small
print...

Cheers.