At last some progress. Hornblock cutouts for the front 2 axles, and some new brass spacers. The problem of sideplay for the rear trailing axle gave me some concern and in the end with heart in mouth I cut the back end off each frame, pre-assembled the rear parts with an old 00 gauge spacer, and then used some hefty brass strip to re-attach the 2 parts of the chassis. The rear part is now some 2mm narrower than the rest of the chassis so hopefully this will give sufficient sideplay. The big holes in the frames were for the intended turned 00 gauge spacers and will be filled before assembly.