I had low pressure from the rear jet & washer fluid running out of the nearside rear corner so took a look at it today.
I had to remove the CD changer and cage and then loosen the sub. There was no way the sub would come out ('52 plate S3 Bose) but I was able to get it lifted up enough to get to the loom that contains the washer jet connection. I found the connection popped slightly apart but not fully disconnected. I adjusted some of the loom securing points and moved the connection up so if it happens again i won't need to loosen the sub as that has to be one of the trickiest jobs i've done, there is a securing nut at the bottom under the central locking pump that is very difficult to get too, my hands are scratched to pieces !!
All re connected and put back together, everything seems to be working ok and plenty of pressure now at the rear jet.