You can actually convert this Class 11 to EM by simply moving the Heljan wheels out to EM back to back, and they run perfectly well.......I've done it!
You will have to move the side frames out, but that is not a problem. Remove the brake sand bins from the outside of the side frames, they just need prizing off as they have two pins holding them on. Under each of them is a screw. Undo the four screws, and the frames will lift off, although the front footsteps will probably need removing and moving out a touch too.