Sorry Doug, only just seen your post.
Yep, banjo bolts are M10 x 1.25 - just got some supplied with my new HEL clutch line.
As an aside, looks like HEL have supplied me with the wrong type of fitting for the slave cylinder. They've given me a 70 deg fitting when in fact it perhaps should be a 45 deg one. Even a 20 deg one as per the master cylinder end would do the trick.
FYI, these bolts also fit the blanked off mirror mounts on the brake and clutch master cylinders but they have to be cut down in length. Useful for when I fitted my heated grips control.