When I worked in the Firestone Tyre and Auto store, many moons ago, we did shed loads of Mk3 Cortina rear axle bushes. I recon just about every MOT resulted in a fail! The first few we did, when the cars were still quite new, we did by burning the rubber out and slitting the side with a hacksaw blade but that was very wasteful of time so we quickly acquired the spacers and forcing screw kit, relatively easy job after that - just don't let the boss - who latterly would have been me - catch you using an air gun on the forcing screw!