I'm not sure, not having been to the U.K. but it sounds similar. Our local "thrift stores" (aka re-sale shops) include some that support a women' & children's abuse shelter,
the local hospital, the Humane Society shelter (as already noted), and the home for mentally-challenged. Some thrift stores are just "for profit" too, but for some reason I
always find way better things that were donated & I suspect they also come with "good karma".