For what it's worth, here is the cest size/sleevel length chart that I spoke of. This comes from Lochcarron, so it is definitely true for their jackets, and from my experience is also true throughout the industry.

Sizes are given as chest size/sleeve length in inches, for regular fitting jackets. Short will be 1" less in the sleeve, and long will be 1" more.

36/23.5
38/24
40/24.5
42/25
44/25
46/25
48/25.5
50/26
52/26
54/27