I don'e see why it should fail/be illegal because you still have working windscreen wipers.
Having said that it's probably a cheap fix - it sounds like a timer/relay has failed, although it could possible be the switch that's failed. There is clearly nothing wrong with the motor.
It works if you push the lever down - it wipes once
If I click up 1 to intermitent nothing happens
If I click up 2 the slow works - click up to 3 and the fast works
but when you go from 2 ( slow ) to 1 ( inter ) the wipers just stop
where ever they are - i have to click down to once to get them to 'home'
It sounds very much like the switch is faulty; it depends on the car how expensive/difficult it is and I don;t know about your car.
Incidentally, all the MoT testers I've seen test the washers and wipers together by washing the windscreen. If the wipers work then the MoT should be no problem.
the screen wash is done by pushing the switch in. it then sprays the screen and
wipes 3 times - this doesn't work - the spray happens but the the wipe doesn't
you have wipe by clicking once or slow