Help finding a British Film from 00's possibly later that involves allowing a Mother in law to stay, attempting to kill and inheritance

Watched a couple of years ago by accident and fell asleep in the middle and want to know what it could be and intrigued as to what the movie actually was about?

I believe it to be either 2000's or 2010's British movie or Tv British movie. I remember the actor playing the husband seemed a star bigger for the role and film,

Husband business finances are poor and agrees with wife to have the mother in law/ mother stay rather then pay for a home (I think her husband passed),

They have 2 daughters who are not happy with the grandmother staying.

I think the mother in law starts taking over and the parents plot to kill her in order to get the inheritance money, mean while the grandchildren are warming to their grandmother. 

The ending is the grand mother goes anyway from the family home with the children on a coach. Something in the back of my head is telling me the parents die somehow, and I also think the parents argued about money a bit.

If this sounds similar please help, I hate getting old and forgetting things. Web searches are wonderful but without knowing the actors name its a pain.