Update

Plumber came to look at the job today. He is a lot bigger and somewhat
younger than me and after about 5 minutes wrestling with it was in the
bathroom wash hand basin draining. :-)

Now I can get it on the bench, I can see what the problem is. One of the
brushes is sparking excessively, but can I find out how the brush comes
out? Can I hell.

New shower is being fitted Sunday morning.

Dave