The water seems to collect in the outer regions of the front and rear footwells, and also a small amount in the glove box on the passenger's side. Looking at a recent post, perhaps the sealing rubber on the base of the windscreen wiper mount could be a source of the problem? Any advice on this would be appreciated, as I really cannot see how it is getting into the back.
The 'scary encounter' mentioned in the title refers to a braking anomaly which happened the other day. After being dormant for a day in the very heavy rain, I drove to the end of my road and went to brake - only to find that pushing the pedal was having no effect. The pedal was rock hard. However, after giving it a good thump with my foot it appeared that the brakes 'freed up' and I nearly went through the windscreen

Cheers,
Ryan