Sorry to drag this one up, and apologies if I have missed a solution.
Washer jets off and cleaned - not a problem.
Mud flap and wheel arch moved to get to reervoir/pump. With the hose to the washer jets detached it will spray like a demon.
Blew as well as I could down the lines (only got a car tyre inflator). Air comes out of the jet well enough on drivers side, and not much on passengers.
I guess that I have still got a blockage, but is there any suggestion on how I might get rid of it?? Headlight washers don't work, but that has never bothered me (unless it might be a reason for not working).
TIA.