HI Andy
First of all are you losing any water from the rad top up bottle?check level.
secondly does the water in the footwell smell of anti-freeze?
if yes then its likely the matrix has gone.
If the matrix has gone its a dash out job.which is a sod to do.To change the matrix once you can get at it aint bad and a reasonable price.
You could try Radweld as a temp solution this may work if its a small hole whilst you decide whether to tackle it yourself or take it to a garage.
I also had water in my footwell after a heavy rain so it could just be something like finding where water is getting into the car.
Good luck
Dave