Intermittent total electrical failure

[grumpypanda]

Our family Alhambra 1.9 TDI S 2000MY has started suffering intermittent electrical failures that have got worse in their effect. Initial events caused loss of ignition, radio and other electrically powered items for a very short time, with the radio coming back on MW/AM when power restored. Most recent two events have been much more serious and hence I am now looking into the cause and considering garage help.
The car 'broke down' when my wife was driving the car in town - all electrical power was lost and the car pushed to the side of the road. Two minutes later she tried the ignition again and the ignition lights appeared as they should, she started the car and drove 4.5 miles home. This time the radio was asking for the code to be entered, the clock had reset, the tripmeter had reset; it had all the indications of electrical power having been removed for a significant period of time.
I have checked earth side of the battery wiring for obvious electrical problems and not found anything of note. I am suspicious about water ingress being the reason for the problem as when investigating the issue this morning I found water in both driver and passenger footwells (more noticeable in passenger footwell). The water is not engine coolant or screenwash so I am now also hunting for the source of the leak. Can a damp/wet electronic control module cause the problems experienced?
Is it possible that 'drying out' the car will fix the problem?
What are the most likely sources for rain water ingress into the front of the car?
All advice appreciated.

[grumpypanda]

What happened to get the problem fixed....
The car suffered complete electrical failure after being moved on the drive - there was no electrical power to any of the car systems although the battery was known to be fine and all connections looked OK.
On re-checking the fault was found to be a connection from the live side of the battery that feeds the ignition and central junction box.
No repeat of the electrical fault since.

The water leak found at about the same time was thought to be via the pollen filter, but we never proved that conclusively.

[mscnoe]

Re water in the footwells - if this Ahlambra version has the same layout as my '96 Galaxy had then you are correct - water collects in the box at the base of the windscreen - it runs in faster than it can run out of the drain holes which are at the sides and drop into the wheel arches. They get blocked with leaves that wash in or even mud from underneath - poke them out with a torch and a stick and pour in fresh water to rinse and check they are clear. When it rains hard water ponds up and runs in through the pollen filter. Look underr the seats - slide them fully forward or unscrew completely - they used to put the alarm/ central locking control box and a few other things under there and the water knackers them! Carpets out and felt underlay as well as its thick and holds a lot before the problem becomes obvious. I eventually used black silicon to block off most of the long slot the water runs into to prevent it repeating - and added some spacer nuts to lift the electronics up higher. It was lovely in Derbyshire in Winter with windows opening by themselves, inside lights coming on when going uphill and other miscelaneous problems. :aargh4: