I am pretty sure you know that those washer systems did not work like the ones on an average car! if you want to navigate home with a windscreen full of oil, you have to use different methods, I am sure you know there is a compass and an altimeter and you can get bearings from ground control sometimes, other than that, welcome to the world of flying in WW2 without proper GPS and other modern gimmicks that make life easier today....
btw, I got some new books yesterday (LW Crash Archive Vols 3-5) and there are some great pilot accounts in those; one from a ME-109E pilot during the BoB reads along the lines that when his engine received some hits, he first turned towards France but once out over the Channel, he realized that this would be very risky so he turned back and face capture rather than risking coming down in the Channel and with a high chance die there...