I personally prefer to wear a shirt and tie in my work. If I am without my tie, I do not feel fully equipped, as odd as it seems, wearing the tie puts me in the right frame of mind for work.
The BR style caps did look quite good on occasion but they are not always the best of head-gear causing perspiration. I have been known to wear a baseball cap in combination with my shirt and tie when I have been working as a guard on a heritage railway, branded of course.
The casual uniform does not do it for me. Once I was stuck on a train for over a hour due to an animal strike. The driver was to be replaced. Some time later, a man in full uniform proceeded down the aisle towards the cab. I was quite relieved as I knew the man had come to save us all from our travel misery. If a man dressed in the Northern uniform of polo-shirt and shorts had turned up, we would have been none the wiser and I would have thought that it was just some random passenger dashing to the loo due to the amount of time spent on the train.