The country manor featured in the film is Pennsylvania Castle on the Isle of Portland, Dorset, which was built in 1797-1800 for John Penn, Governor of Portland and grandson of William Penn, the founder of Pennsylvania.
The band seen playing in the pub is the cult Leeds band 'The Reacharounds'. Their song "Married To The Mob" (from 2018 album "Guitarmaggedon") can be heard during the films credits and fittingly tells the tale of a dysfunctional family.
The pub featured in the film is the Royal Portland Arms in Fortuneswell, on the Isle of Portland, Dorset. It was frequented by King George III on his visits to Portland in the 1790s and 1800s.