Note that my BD copies the earliest pattern of BD. The field dressing pocket on the trousers has no button and only a single pleat. The jacket copies only the first adopted modification, which was a cotton lining on the collar. Para trousers copy the simpler pattern usually seen in photos. They have the internal knife pocket on the right seam. Cargo pocket is lined with cotton drill. Chamois was a bad idea, as the Paras found out the first time it got wet in the field.
Jackets are sized in between original British WWII leanness and typical modern male obesity, with jacket waist sizes 6 inches smaller than the chest size of the jacket. For the less svelte, I have sizes 44XL-52XL. This size range has a 2 inch taper (48 chest = 46 waist). And for those with no body taper at all, I have a few in sizes 48XXL and 50XXL. If in doubt, order a larger jacket. Remember, these jackets are simply constructed and very easy to tailor.
If you have a significant bulge above your jeans, a long size jacket might better encompass it, although you might have to shorten the sleeves.