Chris wrote:
snip
So my question is, what would happen if I put the pump back in
circuit? I'm confident that the Pandora could cope with the increased
heat demand. But would I be able to significantly increase the water
pressure? Would this have any knock-on effect for my neighbours? And
what would Thames Water say if they found out (and would they ever
find out?)

The basic problem is that if you reduce the pressure in the pipe
to less than atmospheric (as is quite possible to do) that you suck
surrounding water in through any leaks.