Problem solved. I 'de-gunked' the nipple in the bulkhead after removing the Plenum Chamber cover. As said above, partial solution, so then removed the pillar trim above the glove box to expose the pipe. It had come loose from the rubber nipple thing - some water was going were it should be more was spilling out. Reconnected the pipe by pushing it back in and hey presto. Problem solved. Not sure how or why the pipe had come loose from the nipple - maybe a build up of gunk along with excess water but seems ok. Couldn't decide whether I should've glued the two together, but didn't. Lets see how long it lasts!