Have you read Dodie Smith? She's most famous for writing 101 Dalmatians and I Capture the Castle, which is my personal favorite. Blackwood writes about some of the same British-flavored fare as Smith: genteel poverty and middle and upper classes unwilling to sully their hands with actual work. Smith has it presented as a light-hearted romance, while Blackwood is vicious, the dark heart that Smith is either hiding or refusing to acknowledge lies at the heart of such stories.
Great Granny Webster is short and pugnacious. It's quick to read, but that doesn't mean that you miss one iota of the vitriolic lives of the characters.