All this "make sure you check them before you accept them" is fine and good in principle, but what if you've driven half way across the country, say from Norwich to Gloucester? You're not going to want to pop over just to check them, then pop back a couple of days later to pick them up. Nor are you wanting to open them just before departing, as you'd have to wait until dusk to get your bees back into their box. The other aspect is, of course, that if you're a novice you can't reasonably expect to drag a more experienced beekeeper all that way to check for you - you'd be asking them to give up a whole day.
Seems to me the seller has a duty to ensure the product is up to the required spec. Clearly no long-term guarantees can be made, but if the colony was collected on the Friday, driven home, then inspected on the Saturday and found to be starving then it was not in a suitable state for sale.