Thanks for all the help everyone, changed the matrices to be column major which didn't help at first, then found the real bug which made me feel like a total idiot. My program is filled with code to generate the MVP matrix but was missing the single line of code needed to load it into the shader!
Once I added that in it finally drew something and a couple of tweaks to undo a bit of damage I'd unintentionally done while debugging it finally drew what I wanted it to.
Thanks again
Angus