Diary of a Nobody, George and Weedon Grossmith - short, wonderfully well observed, very, very funny. I never tire of it.
Second the recommendations for Saki and P. G. Wodehouse.
My favourite Dickens novels are Bleak House and Little Dorrit. I also like Great Expectations, David Copperfield and Our Mutual Friend.
Persuasion is my favourite Jane Austen novel, followed by Mansfield Park. (Fair warning, most people seem to like MP the least of all Jane Austen's novels!)
Vanity Fair, William Makepeace Thackeray
The Moonstone by Wilkie Collins
South Riding by Winifred Holtby - a marvellous novel from the mid 1930s. Would probably be my Desert Island book.
To follow on from Jane Eyre, Wide Sargasso Sea by Jean Rhys - written from the perspective of the first Mrs Rochester
A Dance to the Music of Time by Anthony Powell - 12 volume novel sequence. I've read it several times. The first time, I enjoyed vol. 1 but I wasn't fully hooked until vol. 3 - it was worth it. Widmerpool, one of the main characters, is wonderfully awful.
A Perfect Spy or The Spy Who Came In From The Cold, John Le Carre