Your pics might be of a Bombus vestalis/B. bohemicus cuckoo? Difficult to tell, did you check the hind legs - no pollen baskets? I have seen a B. vestalis female in my garden recently - they are parasitic in the nest of B. terrestris and there have been a lot of B. terrestris queens about looking for nest sites. Cuckoos usually are a bit later emerging than their hosts, because they need the host colony to be set up and running before they take over. Cuckoos have no worker caste because the host’s workers rear the cuckoo young. Perhaps someone else can add to this? Keep watch for the other cuckoos - B. sylvestris, B. rupestris & B. campestris….......
Thanks urbanbumble. I think it is most like B. vestalis or B. sylvestris but I’m not sure. I was so busy trying to get a decent picture of it that I forgot to look for pollen baskets. Will keep an eye out