[TOMT] Looking for a tv show about an inheritance stolen from adult children by their father's new partner/wife

The actress playing the recently deceased father's new partner seemed iconic. I thought it might have been Imelda Staunton, but I think I may have misremembered the ad.

The ad has this is where she says "it's all mine, and there's NOTHING you can do about it!" And she takes possession of the house, and the adult children have to leave their father's house.

Also, I'm pretty sure it was a British tv series.