Wow, Simos, no one's commented yet? We're starting to slip as a group.
I was going to comment, when you first posted, but decided to think about it for a while.
I don't have many artillery pieces in my own collections. I've got several of the German 7.7cm field piece in review order, from Charles Biggs; some Reeves cannons; some from the old Strombecker sets; and Imrie-Risley kits. But having seen some other pieces online since you posted this, I'm going to go out on a limb and say that the limber in your first and second pictures is from Britains.
he thing that stands out, to me, is the method for attaching the team of horses to the limber-those bend pieces of wire attached to the front. They would fit into holes cast in the sides of a pair of horses. They look exactly like the "traces" Britains used on the coronation carriage.
I'm making a guess, too, that the caisson in your first photo, to the right of the limber, goes with the limber and is also from Britain. I don't know about the field piece in the photo, but I'd also guess that it's from Britain. Looking at those pieces, though, it doesn't look like you could attach all three, unless there is a hook at the back end of the caisson that would allow hooking the trail of the field piece.
Anyway, I hope that starts the ball rolling. We have a couple of artillery fans here, so maybe we'll hear from them now.
Prost!
Brad