Well you may have to do a wee bit of traveling to find one but in my experience ordering a jacket from a website is no substitute for going to a reputable shop and trying one on.

I ordered my PC online and ordered it as a 40 short the same size as a jacket from this side of the pond and it was a wee bit tight, luckily for me my brother has a menswear store and thus he has a tailor who was only too happy to rectify the situation.

I have also purchased a Harris Tweed argyle jacket in a 40 short and it fits perfectly, I was in a brick and mortar store for the Harris Tweed. So I think if you really want to be sure you get the correct fit see if you can find a shop near you and get properly fitted.