Much prefer the TopToy DSTT's - You can put larger SDHC cards in. R4DS's are limited to a max 2gb MicroSD's (35-40 games). Under £5 delivered from http://www.dealextreme.com/details.dx/sku.15613 although be warned, these are likely to be fakes. For original DSTT's, you can get for £19.99 including 2gb MicroSD card from http://www.homeworldz.co.uk/xcart/search.php?mode=search&page=1
Haven't come across anyone recently selling the R4DS III's in the UK (Amazon were a few months back) - The majority being sold now are v2 which are'nt SDHC compatible.
You should probably flag down a sandcrawler on Tatooine and haggle with a Jawa. I'm glad I could be of assistance.