I emailed both departments the whole story and they liaised between themselves and visited the abattoir about a month after the 'event', but of course at the time they visited there was nothing to report (they're cruel but not thick, at Evans).
Within hours after it happened, I called the government vet department for this area, who said that as Evans is so small they would probably only have a vet on site for an hour or so. He suggested that it may well be that the first time we went to Evans, the pigs were treated well (when we were still with them, we were taken away to complete the paperwork straight away) because the vet happened to be there, and on our second visit the pigs were abused because the vet wouldn't have been present... in other words, mostly the vet's not there and then Evans gets away with things.
We were told by Carol, the woman who deals with paperwork and 'helps' unloading at times: "it's either that or you take them home". The pigs were already off the trailer by then, they were freaked out and one of them nearly escaped as it was desperately trying to flee.