National Express are offering a bunch of £5 tickets for a limited period.Small print includes "Book between 3rd and 20th January 2012 inclusive, for travel from 21st January and 14th April 2012".
Any interest? Never been myself, but I believe that there's a fair number of decent pubs. This is more interesting to London and South-East based PuGgers: I'm not sure that you'd be able to get these tickets on cross-country routes (and Norwich is a heck of a long way from anywhere!).