I have a long-time obsession with the character "Billy Barlow". My book about the "Billy Barlow Phemonenon" isn't available easily - can't afford to publish it myself, but I'd be glad to answer specific questions about any of him if anyone's interested. It's a very big subject as it turns out and tangled.

As for the question here. I began looking at early musichall by studying several of the performers. (George Coppin was mostly involved in theatre rather than musichall and he left for Australia quite early - he won't help much here) But there's:

Sam Cowell
W G Ross
Benjamin Oliver Conquest (also musichall owner)
Jack Reeves
William Evans Burton
Also look at actors playing at the London theatres during the early part of the 19th century. They often also played the halls.

Good luck Fay. Cheers, Joy