Is this a viable option for me at my age?
Certainly. I know quite a few instructors and examiners who are 75 and older, so you have almost 25 years ahead of you - a whole career! Many pilots begin instructing only after their active career is over, at 58, 60 or 65 depending on country and airline.
Would schools/clubs be interested in hiring me, particularly given my experience will be limited compared to many?
I don't know what the situation is in the UK, but here in Germany most instructors are freelancers who instruct beside another job or after retirement. Instructing on freelance basis should be no problem at all, and you will have the big advantage to be very flexible with your time.