Leak on drivers side

[Clarey]

Hello! This is my last ditch attempt for some advice before I pay a stupid amount to get my car fixed!

I bought an 09 fiesta TDi from evans halshaw in June and it's developed a leak of some sort.
I'm none the wiser on cars, so don't understand where it could be coming from.
It's on the drivers side, mainly at the passenger footwell, but it's damp at my feet too, there's also wetness under my seat. The passenger side is fine. I've been told this is a common fault with fiestas, but just want some advice so that I actually sound like I know what I'm talking about before I take it to the garage. Sorry if my issue seems a bit vague, not quite sure how else to describe it! Soooo..

There's a leak on the drivers side, where could it be coming from?

Thanks