2F

What do you think is going on between Carla Sawyer and Francoise? Why would Francoise think Carla had killed Mr Jones?

I’ve stated my theory on this previously, I believe the college has a sideline in offering students for (underhand) marriages to immigrants/refugees so that they can supposedly legitimately stay in the UK.
Françoise is rightly afraid of having taken part in one of these marriages, I suspect under extreme duress. And everything has now escalated due to the killing of ‘Mr Jones’.
I’m not sure why Françoise would necessarily suspect Carla of having Jones killed.

I agree with >2 Sergeirocks: I believe Carla is running a prostitution ring by using the school as a front.

All of the above makes sense to me. I think that Carla's legitimate language school is failing and she is making money through these means.

I think it’s more likely to be the marriage angle rather than prostitution, but nothing would surprise me about what Carla Sawyer is behind. Carla is obviously connected with the marriage with Mr Jones, but why Carla would want to kill him i don’t know. Not convinced at this stage that Carla was a killer - too much effort for her!