[Nobby]

A quick look at an online TV guide (tv24.co.uk  ) suggests it was this episode, the final one of the first series:

uktvplay.co.uk 

I just started watching. I heard two effings in the first 5 minutes.

At 1:46, a man is chasing a Santa Claus or Father Christmas. The Christmas character is singing. After he sings "Jingle Bells" the chaser says "OK, come on". Both lines are subtitled but between these two lines, the chaser, frustrated at his inability to catch Saint Nick, very clearly says "effing...". This line is not subtitled on UKTV Play. No doubt about it though, it's definitely "effing". I would have added the word here too if I was working for Red Bee.

Admitally, there is a very small possibility that I might just be hearing what I want to hear.