Went to pick up the pump today and it turned out to be ceased. The motor hummed so it was making the right noises. opened it up and the cast iron body had corroded where it had been stored with water inside.
I wondered if I should ask for a discount due to its non operation, but as it was only eleven quid I thought it was a bit cheeky. I said I'd take it anywayand the chap said "OK, make it a tenner then".
A couple of minutes work when I got home saw it running perfectly, so a good result and it looks like I may be able to graft it into my system without too much re-piping.