Ah a lot of information here under the Dahon Spares and Accessories link.

Looks like there are some differences including using a different retaining bolt dependent on if the forks are aluminum or steel

mmm seems seems TERN forks won't work and even for Dahon forks many have different length top tubes/fitting dependent on year.

For now I will play around with the gearing (I want to try a SRAM A2 and SRAM T3) and come back to the fork issue later.

Jerry