If the washer jet moulding is clipped to the wiper arm disconnect the pipe and if you look closely you'll usuall see a wrap over fold in the plastic fitting that you can prise off and remove the jet block entirely from the wiper arm.

take it inside poke through all the jet holes with a pin then reverse flush down those jets via the houehold tap...put the sink plug though in if you drop it the thing might disappear down the plug hole.

before refitting operate the washers to blow anything in the pipeline clear reconnect and spend a few minutes setting up the washer jets with a stiff pin so they squirt in the direction you want...take into account you want the jet to still hit the screen at 70mph as well as walking speed.

If the problem happens again shortly then its possible the washer bottle needs cleaning out, they can get quite nasty inside after a few years, i have no idea has easy access to the washer bottle will be, probably awkward.

Thank you for all your replies and apologies for not replying sooner. It is squirting fine, just not in the right direction! I will have a fiddle with it, it might just need re-directing.