Reverse Light Staying on

Hi

I have a 1991 Ford Fiesta Flight. I was stopped today by a very friendly traffic policeman (who thankfully didn't give me any unwanted points on my license) and informed that my vehicle's reverse light is staying on - which it is. I have been told that the problem may be to do with the reverse light switch. Is this the likely candidate? if so, where can i find it and what's the best way to solve the issue?

Thanks in advance.