"Fuck" is excessively used in every episode alongside some cleaner derivative alternatives as well.
[Series 1]
While not aggressively directed, the main protagonist peppers her speech with coarse language such as 'f**k', and derivative variations of it such as 'bucking', 'fracking', etc.
[Series 2]
There is religiously profane language in this season.
Aside from this, there is some coarse language in this season.
[Series 3]
There is coarse language in this season.