The wipers work on RAY bit they only wipe a small section of the screen so tonight I though it time to pull it all part and find out why, I suspected it was the bushes, but they ll turned out to be like new.
I stripped the wiper mechanism to pieces cleaned it all up, greased up the links, the bushes were like new. I noticed the motor had come loose on its three screws, and one of the wiper spindles was almost seized. Five minute of working it free with oil and it was nice and free. I resembled the whole thing and bolted it all back in place. Now the wipers wipe the screen a lot better than i ever thought possible.
The heater matrix unit needed to be fully removed to undertake all this and its given me a chance to check for leaks (none found), so its all gone back together with new hoses and jubilee clips, and a replacement heater valve. Although I think I might change it for a chevette plastic one soon as they are a far better design.
All in all a good day.