How to replace oven door roller assembly in Britannia Si-9TF-SS Range

I took a chance and ordered a new roller unit although the supplier advised it would not fit my Britannia cooker S1-9TF-SS. In fact the roller assembly fitted IS the same but the hole in front of the roller assembly (in cooker body) is 2mm too narrow to remove the old unit.
I removed the screw (1) holding the old assy and pushed it back into the oven side.
I then filled the slot in the side of the oven, taking 1mm+ each side until new assy fitted through. I used a stiff wire hook to hold the assy so I could pull it back into place, replaced the screw and I now have a working oven door. Espares part was better than old unit and I will now replace the roller assy on the other side of door. The small oven door does not get much use so still works fine. Job took about 1hour plus and a bit of bad ******