ok, first thing - locate washer motor (on the washer bottle) remove the plug, remove the pipes, pull out the motor. watch your screenwash pee out on your shoes (i did that
) remove the strainer from the pump, small and black and made of rubbery stuff. clean it out, and clean the impeller on the pump with liberal splashings of water. check free to turn.
next, clean the connections on the motor and plug it back into the loom. now test it to see if it runs without being in the washer bottle. if it does, replace everything, and fill up the washer bottle. job done.
if it doesn't run, test for power at the plug. if no power, check fuses and wiring. if power, motor duff, buy new one.
if it does run, but no water getting to screen, follow the pip[ework, disconnect at next union, test, repeat, until you find the blockage point. it might be the 't' piece cum non return valve is duff. if so, go to halfords, buy t piece, and non return valve (couple of quid) and fit into system. test it, and hopefully it will all work.
if all the above fails, let us know, and we can scratch our heads some more
hope it helps.