Saw a 'pay to weigh your baggage' scale at MAN recently. Simply went to an empty check in desk and used their scale. No hassle, no inconvenience to others and no money changed hands.
Never even thought of the possibility of doing anything different. Also has the advantage that you are using (presumably) accurate scales. Use a portable hand-held scale at home and in hotel for a check before going to airport, though.
UFO