I had the MOT place argue my cables were stretched but after really taking some time to make sure the drums were clean of dust and the shoes were centralised and manually adjusted as close as possible to the drum surface without binding the handbrake is totally fine again.

Before adjusting the shoes you have to make sure the cable adjustment is slackened off so as not to be applying any tension to the shoes otherwise you cannot adjust the shoe clearance properly. People often make the mistake of taking all the slack out of the cable and then the auto adjusters on the shoes cannot work properly.

I don't believe in the stretching theory.