apologies for the delay in replying.
You are absolutely correct!-all the bees in your photos are Male Red-tailed bumblebees (B lapidarius)
For exactly the reason you stated- the tail length (the number of segments covered by red) is intermediate between the short tail of Early bumblebees (B pratorum) and the long tails of Blaeberry bumblebees (B monticola).
Males of this species (B lapidarius) always have a yellow moustache, a distinctive feature of males of four common species.
The individual in photo 3 is still in fact a male. The tail may look pointy because of the angle but it does not possess a pollen basket. Males of social species don’t have a pollen basket but short hairs over the surface although there is still some bare cuticle ( so alot less hairy than the male cuckoos). This segment of the leg is much narrower than in females.
The red-tailed bees are indeed confusing but you are clearly getting to grips with them.
Thank you Elaine. Need to do more work on pollen baskets, but meanwhile can send my beewalk report!