There might be some argument there.
But...the IG don't seem very British. Of the regiments GW has ever done much with, you have Mongolians, Russians (both Soviet era and Tzarist era), a Middle Eastern one, a Vietnam era US one, a WW1 German one, a WW2 Afrika Corps one, a generic modern weatern one, a USMC in dress uniform on the parade ground one...yes, there's an obscure Zulu Wars era British one, and the MkMarty Sue Tanith one, which maybe sorta is scottish, a bit.
GW seems to think that foreign (or at least foreign sounding) influences would be more interesting. It's Blood Angels, not Blood Angles, after all.