I had another go with the SRAM card I bought yonks ago, I still haven't managed to access it in my laptop.
I found this page, with some details on editing the /etc/pcmcia/config file.
So I tried that, I added:
card "SRAM Card"
version "SMART Modular Technologies", " 4MB FLASH Card "
but had no luck.
I give up. I can't believe it's this hard, I should just be able to plug the card in, and have /dev/mem0c0c or something turn up.