Personally, I think the piper would fit right in at any evening function today - which suggests something of a 'timeless' quality to his outfit, even if it is too modern for the 1914 setting. This was probably what the film producers were banking on.

There is nothing remarkable about the factor's outfit - except that his tweed coat is probably closer in style to the setting era, and that, too, would not look an inch out of place today. But he does seem to have a stud-on collar with rounded corners, which is more in-keeping with the pre-WWI setting.

OC is spot on with actors wearing their own clothes, even when playing more than an extra role. Desmond LLewelyn, the actor who played the gadget-providing 'Q' character in the early James Bond films, is known to have worn his own old tweed suits, that helped give his character more authenticity and credibility.

I had school teachers who dressed in much the same way back in the 1960s, so having the actors comfortable and in a recognisable, natural 'lived in' outfit must be a benefit to both the wardrobe department and the director.

I know a couple of soap-opera actors actors who receive an allowance to buy their own 'work' clothes, so that there is a degree of continuity with their appearance. It makes perfect sense for the wardrobe dept. to encourage it.