If the wheel is getting warm and the lever's not moving, it looks like it's sticking on, on that side. If it had been doing it for the MOT, it would've failed. It could only be the caliper or cable. Easy to pop off the cable connection and with the help of an assistant check it's not the cable. You should be able to pull it back to off after it's been pulled on. Might just be a dodgy cable. I would advise leaving a bit of reserve travel on the handbrake, as it helps the adjustment mech work better. You can always adjust it up for MOT time, then ease it back off again. I used to cheat on the 8 by winding the piston out till I had a 2 click handbrake, then wind it in a quarter turn or so put it back to normal. A screwdriver fitted the piston cut out perfectly, so the whole process took about 90 seconds with no need to jack the car up or remove wheels. Obviously there was no anti rotation pip on the pads. I once had a recon caliper that didn't adjust, hauling it to bits revealed that whoever put it together assembled the thrust race put the outer tracks on the wrong way round and the increased friction in the bearing stopped the mech adjusting up. It's a poor design really.