The pressure will obviously be more with the pump running, therefore
more chance of leaks. I would be inclined to fit a 13amp plug on the
pump system and plug it into an extension to try it. Be very careful of
the earthing arrangements and do not be tempted to do any more than
test it with this arrangement.

It depends on where the pump is.

Mine is in the airing cupboard in a bedroom. I changed the immersion heater
FCU to a fused one, spurred off a 13amp outlet, and connected the shower
pump using a 3amp plug top for ease of connection and maintenance.

If it's in the bathroom, I would connect to an unfused, unswitched flex
outlet, running off a 3amp switched FCU somewhere accessible outside the
door.

If the supplying circuit is not RCD protected use an RCD FCU. See
http://www.screwfix.com/app/sfd/cat/...14770&ts=21503