In addition to the above I have today removed housings on both sides (on top of which sit the microfilters) revealing on the drivers side, the brake fluid reservoir and servo and on the passengers side a large plastic box. On the drivers side the rubber bung/drain plug, which is tricky to access, was partially blocked but did eventually allow water (which I poured in) to drain away, I cleaned the drain as best I could, forcing a plastic tube into it and that side now appears ok, for the moment. The passenger side (which is the problem side) however is another kettle of fish, the bung/drain is impossible to access without removing the plastic box (which looks to contain electrical stuff, It is not obvious how this box is secured). I did consider pouring in some water surrounding the box to see where it came out but decided not to tempt fate. There didn't appear appear to be any water in that compartment but it might of course have drained into the car!

If anyone has dealt with issue before, I would appreciate your advice, ideally I would like to remove the electrics box if its not too difficult.

Thank you.