Hi Pat,
Yes, I would imagine with a 6pdr Churchill or Cromwell the cases would be fine. They are the later pattern, I'm not sure at which point the change in style occured. However, if you needed early style Resicast do a nice set of cases but without decals.
early 6pdr ammo cases
https://armorama.kitmaker.net/review/3783 They also do a set of 6pdr ammo (late) too for their gun but I haven't gotten to reviewing it yet. So there is good choice out there. These are cool though, Derek makes some cracking ammo sest for his guns.
Al