it crawls across, it doesn't stop at all, just goes VERY slow, almost like it's far too dry to move. Even in torrential London rain!

It just started to do it one day, didn't slow up, just switched to the fastest speed and it hardly moves - very slowly moves.

It doesn't seem to slow up at any point, it's too slow to do that - I know what you meant, does it start fast and slow in the middle of the screen etc. but as I say, it's just extremely slow, much slower than the normal slow speed.

It's a single blade 'panoramic' wiper (I think that's how they are described!). It used to rock the car at traffic lights! Now it isn't worth using.