Just some info if someone has experienced similar problems...
This filthy weather means I'm washing my rear window more often now.
So I wasn't best pleased when the system suddenly stopped. I could hear the pump running but no water at the tailgate.
Luckily it hadn't been raining so i noticed the dribbles of water at the gap where the tailgate meets the bodywork.
Popped of the cover to the rear wash-wipe and then carefully removed the rubber concertina hosing between the body and the tailgate (passenger side) to discover that the washer feed pipe had failed where it had been bent and unbent opening/closing the tailgate.
Short trip to local autofactors and for about £6 I replaced a length of original hose (quite tough to bend) with something a little more flexible and a couple of joiner/couplers. Job's a good one and the rear washer works again.
Keith