F3G 
I had just written an almost identical post but my computer (newly upgraded) is unpredictable on what it allows me to do on PPrune at the mo or perhaps it has ash contamination
The post has disappeared when I pressed submit
10Downingstreet at my mob the elderly in our training acronym says "elderly if frail" then you cannot sit by this exit. We go on physical ability not age. Age discrimination is against the law.
Make no mistake here safety not comfort or revenue is the consideration at these exits which are unmanned by the CC during takeoff and landing....the very times an incident is likely to happen. If you or anyone does not appear to have the physical capacity to man these exits at these times you will be challenged and possibly moved by the CC....regardless of age.
I think this would apply in all UK airlines. With the greatest of respect to our ground colleagues many do not know what applies on board. The marketing depts of most airlines will capitalise on the revenue provided by these seats and consider nothing else at the time of booking.....
Who sits at these exits is at the sole discretion of the CC in accordance with company policy.... end of. That said it does appear on face value Thompson CC could have handled this better and more sensitively.
Personally this is an area which I think we could all brush up on in initial training.