In the end I had to write my own library of subVIs making .NET calls.
I got there by following the C examples from Pleora.
For the daisychained through CameraLink comms, I had to invoke a virtual serial port bridge using software called com0com. This makes two virtual, connected serial ports, one exposed to Windows calls as usual, the other end 'connected' to the Pleora framegrabber.
Quite a lot of stuff to sort out and .NET handles to manage.
I'll see if I can upload the library of subVIs but can't upload the main programme.
Thanks SDC. I'll definitely take any examples you can send. I had read about the com0com possibility but I was hoping to avoid another software. I have to get gov approval for all of the software. If you get a chance to post some examples I'd be most grateful.
BTW I contacted Pleora and their customer support is definitely sub-awesome.