These things are called shower booster pumps. There are plenty of them that operate from 240V without an isolating transformer - here is the instructions for installation of the Wickes version.
http://www.wickes.co....ces/images/gil/46.pdf
Since it is a fixed electrical installation it should be wired via its own fused socket, with (probably) a 5A fuse - depending on the rating of the pump. Clearly there should be no access to the pump from the bathroom side.
Often the pump is mounted in the airing cupboard - have you actually bought the new pump?
I use a stiff length of steel wire hooked at the end to pull cables through partitions - assuming there are no studs in the way.