We never seem to get a uniform at my TOC that is just right, and that's after having clothing tested for several months by individuals from all different grades of Drivers, Train managers, Catering, Platform, Ticket office and so on.
Obviously everybody is different in body shape and would be too excessive and expensive to have tailor made uniform and unnecessary.
Also those that are dealing with passengers should be smart, be easily identifiable as to what train company they work for and job title.
Drivers just require something comfortable, fit for purpose with adequate pockets for all the keys and diagram, phone, diary and other bits and bobs we need, so smart trousers with elasticated waist (we do tend to spread out a little), well i do! Polo shirt with company name, light jacket for warmer weather and a good all weather coat plus safety boots/shoes.
One of the main requirements though is to be able to distinguish different grades but most importantly those that are competent in PTS (Personnel track safety).