Are the old ones completely shot?? just theres 2 adjustments that may get it through the MOT so you can find the right parts after, one on the wire under the body where it comes from the hand break then into a junction where it splits into two and then there is adjustment in the hub itself which is a threaded bolt that pushes the shoes further out.

I replaced the rear brake disks with UBS25 trooper ones from Milner off road, maybe their shoes will fit?