Thank you VERY much for your help.
Matt and Richie, You're stars. Switching LOCAL off on the M1 solved the problem.
Chevytraveller and The Elf, You're right. A photo or simple diagram would have been a lot more descriptive than my mumblings. I'll certainly remember to include that if I ask for help again.
dubbmann, Sorry for not explaining myself very well. M1 as a controller, paired with the 1080 and the K49 (controller)paired with the M1.