Getting confused over white tailed bumblebees

Hi Helen
I'm not sure how helpful this will be but your top photo is one of the Bumbus lucorum group which contains three species, the other two being B. Magnus and B. cryptarum. The later two are both from the highlands, B leucorum is common over lowland Britain but due to confusion with the other two species means its status in Scotland is uncertain.
The middle photograph is either B. hortorum or B. jonellus both of which are fairly widespread in Scotland, both have three yellowish bands, two on the thorax and one on the front of the abdomen.
The third photograph is a Cuckoo Bumblebee, these can be tricky but is the commonest one in Scotland and does parasitise bees of the B. leucorum group.
If Matt Smith or Stuart Roberts see this they will probably of much more help.
Kim