Brake lights sticking on a rover 75?

While this may not be the answer for your specific problem, many times British electrics are unreliable. Disconnect the switch from the mounting bracket and see if it sticks without the pedal trying to work it.

Another common problem is wear, many switches have adjustments and as the plunger wears, the switch has less and less travel, eventually causing brake lights to come on unexpectedly.

Finally, it is not uncommon for debris to get into the pedal or linkage, or the return spring to come off or break, when that happens pedal travel can be restricted as the pedal will not return to the proper rest position. This is VERY BAD since sometimes it can prevent the brakes from releasing, causing premature wear, poor fuel economy or brake overheating leading to failure.