The central heating pump is dead. Even connected directly to a 13A
plug it does nothing. Previous owner claimed to have a British Gas
service contract. Haven't heard anything about that or attempted to
keep it going.

The pump says:
Multihead III
British Gas
Warranty Date 301110
Make by Circulating Pumps Ltd PE30 4PP

So apparently in warranty - but who's?

Searching on the web, it sounds like these might not be very good.
Shall I just buy a Grundfos, or are there any tricks for coaxing this
back into life?

Cheers,
David.