Ah, i think I have it working, I have set the SSPSTAT and SSPCON registers in the pic, and have it in mode 0,0 at Fosc / 64, though this was just to make monitoring it with a logic analyser a bit easier. The MCP2515 can handle either mode 0,0 or 1,1 and at up to a max clock of 10MHz. as the crystal for my PIC is only 10MHz, thats not going to be an issue.
the SDO line is always driven low, but I think that has was being caused by issues within the MCP2515, ie the control registers not being correctly initialised.
If you / anyone knows the MCP2515 I would be grateful if you could look over my code, tell me if I'm making some stupid mistakes, as I inevitably will be, lol.
Cheers
Sam J