Having poisonous plants in your garden is only evidence of having a garden. Most plants contain some kind of poison (it's a survival mechanism) eg, over 2,000 fruits and vegetables contain cyanide, and plants like deadly nightshade and wolfsbane can be found all over, as well as growing wild.
When Sister Boniface was at Bletchley Park, she called the supervisor "Mr. Turing." The real Mr. Turing was a code breaker during World War Two and died in 1954. This series is set in the 1960s.
The newspaper headline shown in the pub at the end states is The Good Samaritans'. The apostrophe is an error and any journalist, editor, and typesetter would know that it doesn't belong there.