I actually thought the shoulders were, if anything, a little short, but maybe the shoulders could be brought in a little on the left side - that's my shorter shoulder. PJs actually measured me for my jacket at 19.75". I think they do that based on where your upper arm/shoulder muscles end, though, and not on where the point of your shoulder bone is. Tom there told me that my upper arm muscles added considerable to that measurement, so maybe it needs to be a bit shorter for a shirt as opposed to a jacket.
Based on that post Luxire has already suggested an alteration they could do to my pattern to remove the crease below the shoulder on the back view - they are good like that
Jason - thanks for clearing that up RE the waist measurement, hadn't even thought about halving the 3 inches!
Turns out it will cost more to enlarge the shirts than I had though, so maybe I will just live with it/lose some weight and order some more with slightly more generous measurements for the winter months...