Don't use the flat plates welded under the end of each sill, Haynes incorrectly lists these as jacking points in various manuals. These are called slinging shoes and were for moving empty shells around the factory and sometimes for tying down Minis when they were shipped. Thay are not for supporting a fully built car and will simply collapse.
As said above either use the Mini standard jack in the jacking points under the doors, or a scissor or trolley jack under the flat areas of the subframes. You should jack below where the subframes have vertical parts above these flats.
As I thought, they don't seem designed to take the weight of a car!
Car is safely jacked and the wheel is off

!
Was a sharp stone chip between the rim and seal/bead . . . was really wedged in there and has almost sliced all the way through!