Go smaller than larger if you're unsure. The overcoat is huge and the young lady in my class had to wait a while to swap it down 2 sizes!
The harrington jacket doesn't fit me. I ordered a large like I am in most clothes - the length and sleeves were spot on, but the body was like a flapping bin bag. I was relieved when the zip broke and the pocket linings tore through - as I reordered a new one in medium. Still too big around the middle! and the sleeves stop half way down my forearm.
I have since invested in some V neck jumpers from primark to wear instead.
There is some give in the trousers due to an elasticated bit: probably a wise design initiative to stop them ripping as peoples' bellies grow
cheers everyone