Thanks for the comments, the idea it could be down to the screenwash hose is plausible - I have never felt the rear jet has forced the water out with any great deal of pressure, so maybe that is part of the issue.
Yesterday I tried to open the casing by unscrewing both of the bolts; maybe there is a special technique, but I couldn't get it to budge. I did note however that there was a lot of water/moisture in and around the edges of the casing.
Funnily enough, it has worked absolutely fine again from yesterday morning onwards! But have got an auto electrician coming today to have a look, so hopefully we can nail down the cause.
Yesterday I tried to open the casing by unscrewing both of the bolts; maybe there is a special technique, but I couldn't get it to budge. I did note however that there was a lot of water/moisture in and around the edges of the casing.
Funnily enough, it has worked absolutely fine again from yesterday morning onwards! But have got an auto electrician coming today to have a look, so hopefully we can nail down the cause.