That's a hard question to answer, because history has spat out so many fantastic British writers.
I love Dickens, Austen, Hardy, the Brontes, Shakespeare (I'm a classics nut).
My favorite book of all time is Tess of the D'Ubervilles by Thomas Hardy but if I had to chose an all time favorite writer, it'd be Jane Austen because I've never read a bad book she's written. She writes so beautfully and really sucks the reader into the world she's created.