on the p38 one of the sliders on the bracket seize and dont let the brakes balance properly, this leads to a LOT of squeaks and grinding noises.
i refurbished mine, all 4 of em, broke one of the sliders and had to drill it out.
the rover 75 are the same and are a good replacement slider, they also suffer from the seizure. plenty of copper grease and regular checks on em!!
dunno if its true of any other landys but i suspect it will be as they are in rovers and the rear of some mg's, poor manufacture basically!