Organisations:
Dawn Duellist Society - Foremost HEMA group in Scotland based in Edinburgh
Aberdeen Swordsmanship Group - Fiore’s Longsword (Italian) but with an Aberdonian accent.
British Federation of Historic Swordplay - Of which GCoD is a proud member.

YouTube footage of HEMA Longsword:
Instructors of the Association Zornhau
TheRealGladiatores - atmospheric authentic combat
TheRealGladiatores - more atmospheric authentic combat

Forums:
Sword Forum International - Foremost forum for sword related discussion
MyArmoury.com - Forums and a great resource for sword related articles.
Martial Arts Planet - WMA forum used by GCoD for a good argument

HEMA compatible Sword Suppliers:
ArmourClass - Well thought of Scottish supplier of swords to the HEMA community
Kovez Ars - Czech swordsmiths who supply munition style weapons
Tim Noyes/Heron Armoury - Excellent custom Swordsmith within the reach of mere mortal salaries

Research materials:
Schielhau.org - Foremost repository for German Swordsmanship fechtbücher (Treatises)