Very sad that the smarter dress only applies from Monday to Friday. At my unit, we had many visitors at weekends too, when traffic loadings were lighter, and the chances of distraction were lower.
'Trainers' denims, flip-flops and 'hoodies' should really be reserved for night-duties.
I had the pleasure of visiting EGVAZT during Sunday's RIAT a few years ago. All the volunteer ATC staff were 'smart-casual', in custom polo-shirts.