Thanks for the ideas boys, but I have already done all of that.
What I want is to work out the trigger mechanism and hose. At the moment I have a pole with a nozzle on the end and the hose threaded like a normal wfp. That is the easy bit.
The trouble with that is that I need two hands to hold the pole and another one to operate the trigger.
My latest idea is to take an old pole and cut a slot in the base section, so that when it is extended the hose will pull the trigger into the slot at the base where I can operate it with both hands on the pole. I would need to use that pole at full length for that idea to work, but that is not a prob as I have several pumps and short lances as well.
I will get round to it in the spring when it is a bit lighter in the shed.