Make the guns free, or increase the call-in range to sight range.
The guns themselves could probably use some help too.
Making the guns free doesnt do a thing. The brits need effective artillery that isnt castable from grenade range(even if it makes it buyable in tier 3).
Just a FYI, the Sexton has 2x Less AOE than a 105, fire only 5 rounds(10 with LEF18 and 7 with Priest),has a longer cooldown than the LEF18 or the Priest, alot smaller range, same CP requirement and has extremely big veterancy requirements. In 15 games with royal arty i couldnt get it to vet 1.