Nice one Rick01, was going to post the same as I've just had the blocked filter disease! Jumped the gun a bit by ordering an aftermarket pump and 18mm seal from fleabay so I swapped in the new seal and pump after flushing out the tank, aftermarket seal is just a grommet and has no filter to get blocked so the jets would be the next port of call for gunge, but at least they're a bit more accessible than the pump!
In case anyone wants the model numbers for a genuine ford washer pump mine is a W Reg Escort 55 Van and it's a 93BB 17K624AA D00LA 0BA, the aftermarket one was about £5 and the seal £1.50 as opposed to dealer parts prices, make sure to get the one with the correct electrical connector, later cars have the angled electrical connection with a wire clip as opposed to exposed spade terminals pointing straight upwards. It also needs to me an 18mm inlet and single small bore outlet. Hope this helps someone.