Matrix, that's great. Never heard of this MMM. Any chance of his name - if you have the issue that is
CB+ only has 2 issues of Bullseye on file and both are from 1931. As Bullseye is very difficult to find, I've little chance of finding out more, and there's nothing on Friardale.
Those ancient French comics are also like hens' teeth. There were a lot of Masked Mystery Men in European comics in the '30's, '40's, '50's, particularly in Spain, Italy and France.
As you mention British storypapers, I should mention that there are many other heroes/MMM in them. If you know all this, sorry for boring you, but I am a superhero/MMM nut. Various papers had characters like The Black Whip, Flaming Avenger, The Iron Man (from 1st. World War), Hooded Unknown, The Night Hawk, Zero the Silent, Son of the Electric Shadow (text strip and his dad was a villain

), Karga the Clutcher (villain as hero), Phantom Avenger - well you get the idea.
I had hoped that more members might have added some comments to this post, so thank you for jumping in.