Hi Andrew. I have tried so many different PCMCIA cards and adaptors it's enough to make your head spin. The short story is that most do not work.. I now have a simple kit that I purchased from the UK that allows me to connect the parallel cable from my modded SPC900nc to an adaptor that gives me the choice of Serial connection or USB, and it works well.
Do a search on E-Bay under SPC900nc and you will find on for sale that does the job fine. It has been made for this job, and I am sure it will solve your problem.
Regards
Mardy