So a little update on this for anyone who is remotely interested....
The car is now DRY, completely. It took a while to dry the boot compartment completely, as the foam around the hydraulic pump was sodden, so kept releasing more water once the bottom was dry. Took nearly two weeks.
I have noticed that the later cars have a re-designed foam piece, so the pump motor sits
on a foam piece, whereas our previous 2013 car didn't have the extra piece at the bottom. Maybe BMW did this to help protect the pump from corrosion
when water gets into the boot (rather than if).
I am not 100% sure how the water got in, but have a theory it was a combination of lack of maintenance to the rubber seals and cleaning the car with a pressure washer.
I also think the rear bootlid wasn't pulling down enough on the seals, so have adjusted this a little.
The cabin was also damp, but not wet. There were drips coming from the sun visor area along the top edge of the windscreen seal, along with quite a bit of condensation in the nearside rear light cluster (but no water as such).
I have gummi-pfleged every single rubber seal on the car, most were pretty dirty and a bit dry, so a sign they had not been done for a long time, if ever!
The car has been out in the rain since and left out in the rain with no new water anywhere. The inside has dried up and the condensation in the rear light has all but gone. I have a half cover which has been used already and will be used whenever heavy rain is forecast, just in case.
I will be keeping a close eye on it and re-siliconing all the seals in a few weeks. Hopefully that is all that is required.
I have yet to find the additional speakers, though!
All good things come to those who wait. I'm really impatient which explains a lot.
F31 320i. Good car.
E89 20i Now fully dried
Z3 'free litre'. Project and a half. Complicated!
Mazda3 sold
Tatty old R56 Mini Cooper. Money pit!