Thanks for your help guys, I've just pulled the carpet out and no signs of any coolant. Everything's dry and no signs of any previous leaks either.
I had a look at the coolant cap and the part number on it is 996.106.447.01 so looks like that needs replacing. I then lifted up the plastic horizontal plate and there was lots of signs of moisture and coolant in the little gaps and corners so definitely looking like it's the cap. Will get a new one ordered asap
