Yep, Mercia is the valour bonus region for Billmen, Wales for Longbowmen.

SlyConqueror: Are you running a modded game? Since Longbowmen from Wales and Billmen from Mercia are coming out valour 1, while Sergeants from Mercia have valour 0, that suggests the region bonus is working fine, but the bonus for Master buildings isn't. If you aren't modded, then I can't think of a reason why your Master buildings aren't working correctly.