Hopefully you don't read this message too late!
The Geological Society of London, through its bookstore service, offers periodically at a very low price different volumes in an online sale. The volumes belong basically to the Special Publications series, amongst others.
In this occasion the GeolSoc runs the sales from 30 of January to 6th of February of 2009; but don't worry, this sales are repeated every 2-3 months.
This time most of the books are offered at £25 (sales price for the last years, as far as I remember), and having in mind the quality of the titles, this is a real bargain.
Check it out here: http://www.geolsoc.org.uk/gsl/publications/bookshop/SalePublications