Thanks for the suggestion, I have another one of these on the way:

NEW FTDI FT232RL KKL USB OBD ODB OBDII OBD2 INTERFACE - eBay (item 370453504187 end time Jun-03-11 07:26:12 PDT)

1 transistor, 2 resistors and reprogram the uART and I have another hybrid i-bis and IPNA/Carsoft cable. I installed a wee socket in the last one and installed a plug on a lead permanently in the boot that matched. Its the devil I know.

I suspect that my CAN-BUS cable will work with NavCoder, will test it and see.