Our friendly neighbourhood builder has sorted someone out. He said 'between 11am and 1pm', arrived at 11:15, confirmed it's the pump, and has just returned with a replacement.
Update: out of the door, finished by noon. £90 total, including £45 for the new pump.
It's like most of their work - low budget compared with some, no-one who stars on a TV soap - but intelligent and fun stuff for all ages. JoJo loved it.
Ideal for all boys and 'quirrels' (don't ask!) it's on until the 17th.