There are plenty of opportunities if you want to play Arthurians. When I started my project I gave the 5 manufacturers a try listed in the pic above. Sizewise they work together very well, except the Foundry mini which is shorter and not so bulky.
A short overview:
Black Tree: The Late Romans are some of their nicest minis. They aren´t very detailed and not very well casted. But they paint up easy and look good then!
Musketeer: I loved Bill T´s sculpting style from the start. Here you can plunder the new Late Roman, the Saxons and Goth ranges. They fit my painting style, my favourites so far- the only reason I didn´t buy the Late Romans is that I ran out of money this month...
Gripping Beast: Again a vast number of useable miniatures in their programm. They´ve got all the characters from the novels, even Wolftail warriors. Their faces are great, but some poses are a bit weird.
Foundry: The smallest, most expensive in this line up - but also the most beautiful with all their crisp detail and very good poses. You can use the Late Roman range too.
Westwind: Some cool vignettes and character packs. Unfortunatly I don´t like their seperate head system, and the shields are too small for my taste. I use the musketeer ones with them.
There are other manufacturers like Artizan but I didn´t try them, I already got to much in my lead mountain. Hope that helps a bit if you´re interested in gaming this period.