"customers who only want a cup of tea"
But they don't want JUST a cup of tea - they can get that at a Costa for £4 - they want a cup of tea AT OLD WARDEN - to breathe the sacred fumes and look out on the airfield. I know the feeling - when in the vicinity I often manage to stop for a coffee at the 'Bushe Cafe (no extra charge) whereas I'd probably get as good a cup in more comfortable surroundings down the road in Hartley Witney - but no aeroplanes in sight.
The answer is to restrict access to the whole site for those who want to see it and charge extra for those who "just want a coffee" - but not the full price - maybe £1 extra a head?