Have a problem with the drivers side foot well filling up with water every time it rains, from the north of the UK so it rains a-lot...
It is leaking in at the side of the dash board and running down, any ideas would be appreciated.

 

Depending on model year, could be windshield seal, or clogged sunroof drain tube.

 

I own a Toyota Tacoma that had your exact problem. I pulled up the carpet and dried it out and many other things. Come to find out it was the windshield that SafeLight installed the year before. The windshield was not seated properly. They replaced it at no cost.