Shirts designed to be worm without ties are OK - such as Oxford shirts with button down collars. But the current trend of wearing a normal 'office shirt' with a suit jacket makes you look like some sleazy politician and is deplorably scruffy.
Short-sleeved shirts with ties are ridiculous in my view - but quite common on 't other side of the pond.
Berets? Dear me no - not for officers. Other ranks and French onion johnnies only!
Those with long PPRuNe memorieswill recall that one RAFG F-4 pilot actually gave the reason for his leaving the mob as being due to not being allowed to have long hair.....