A Toilet has never been a requirement for a Motor Caravan in the UK.
And I don't see why it should really as if someone uses campsites, they will often only use the camp facilities (there are a surprising large number of people with full on-board facilities who never ever use them).
Why anyone thinks legislating that a campervan must have a toilet will make any difference at all to those people who don't care I don't know? If it WERE a requirement AND campsite owners would only allow vans with toilets, it would be a joke as they provide facilities to those without toilets (e.g. tents) anyway, and there is nobody checking people who wildcamp have ANYTHING in their vans, let alone specific items.
You would end up with a situation where a camper WITHOUT toilet facilities would be forced to wildcamp even though they might want to specifically go to a campsite for those facilities, and then those who want to do the right thing might end up with no alternatives!! Talk about cutting off your nose to spite your face!