So which flying clubs do provide scales for members' use?
There were some at Cambridge Aero Club. I haven't seen them recently, but they were hidden under a bookshelf or cupboard or something, you had to know they were there.
There's always the danger that if you do something helpful like provide scales they'll be removed by some H&S bod on the grounds that they're not calibrated. Thus forcing you to use the bathroom scales at home, which ... guess what! ... aren't calibrated either.