NT,

Can you not upside-down it and pour a new block in situ?
A couple of hours for £200 saved isn't bad.

Thanks, but I'd already thought of that. Unfortunately, it didn't
work: the concrete oozed out of the little drawer where you put the
soap powder. Mind you, there was a bright side: it flowed into the
hole in the floor where I was going to sink the earth rod, and neatly
closed it up.

Bert
http://www.bertcoules.co.uk