Ok I've solved the problem. Removed the bayonet mount from the lens (4 screws). then flipped it over and prized the metal arm (holding the pin in place) very slightly so the pin dropped to a flush level. Didn't have to remove the pin entirely in this case and the lens now mounts fine.
I found this video very useful:
Thanks for your help!
---------- Post added 06-25-15 at 02:06 PM ----------
On first inspection this Miranda 24mm lens seems great by the way.
It has the "A" setting if you want to have auto aperture which is working great with the K-01 and slightly wider field of view plus macro feature is nice too.