Another source of memory cards is at:
http://www.powerinnumbers.com.au/ This gent has a lot of glowing recomendations in DPReview's storage and memory forum. One of them mine.
An example is Ridata CF cards, 512mb at $Aus370 or about GBpounds 128. He also has Image bank storage systems.
I ordered a card on a Sunday and had it in Canada on the following Thursday, via FedEx. Shipping was about $12US. Your customs duty might change the final figure though.
There is a lot of info in DPReview on memory media.