Beautiful conversions and painting! OB, I have spent many hours on your blog; You and I have many common hobby interests and this is yet another.
Many years ago, I played in several GWI games with some gamers in my area. The rules used were a GWI-specific set called "Freedom or Death" co-written by one of the gamers and Spyros Koumousis, owner of Alphacast miniatures. The armies were primarily 15mm Alphacast miniatures (with some Old Glory Turk cavalry). The Alphacast miniatures were somewhat simple but very charming and the range was fairly comprehensive (Alphacast also had a nice Balkans War range). With Spyros' sudden passing in 2006, the range sadly went out of production.
I was fortunate enough that the co-author of the GWI ruleset gifted me enough figures for some smaller armies. I don't believe I have any Philhellenes but not entirely sure as it's been years since I have pulled them out of storage. I will have to dust them off some day.