Looks to me that the uk mirror is outdated and image creation fails because of that:
$ lxc launch images:debian/10/i386
WARNING: cgroup v2 is not fully supported yet, proceeding with partial confinement
Creating the instance
Error: Failed instance creation: Unable to fetch https://images.linuxcontainers.org/images/debian/buster/i386/default/20210507_05:24/lxd.tar.xz: 404 Not Found