Well finaly got to play with it this week down at some woods I own, "Bess" as I call her sings sweetly. I did carry out some experiments against wool etc see what the effects was, intresting 

She's proofed for shoot, I was only using blanks as I was interested in the effects of "blasts" at various lengths on different material, against wool until you are less than a meter burn effects are very minimum but down less than 100mm the blast effects - well holes start appearing, this does not take into account blast effects on a body as the material was just hanging from a branch.
Linen showed burn effects from about 2m but even at almost blank point range no blast hole was made just lots of burns and the material just flew off the branch. Leather suffered burns on the side facing gun but the other side did not show any signs of damage.
This does not take any effects of blasts against solid bodies and the test material could “fly off” as not “fixed”.
So as long as you are not directly in line with the muzzle against “burn” effects as I expected pure wool and leather offers the best protection but even linen will offer some but no where near wool and leather.
So while not very scientific if you are “manning”  the guns follow the rules and wear leather gloves to protect your hands as they are normally the nearest part of you to the “hot stuff” and while not a rule, a layer of pure wool covering the other parts of your body will reduce the risks of burn injuries.

Heath, s'what effectively happened to me at Bosworth although in my case it was a handgonne & the wadding hit my armour - luckily.
The bloke responsible now understands not to point loaded weapons directly at people now though, so that's a plus point.