ok two things:
firstly, substandard goods, however obtained, are covered by Sale of Goods Act 1979 (as amended). If faulty, damaged or not fit for purpose then they should be replaced or a refund issued. That would include death/damage in transit.
secondly, the Consumer Protection (Distance Selling) Regulations 2000 (as amended) specifically exclude custom items (ie you can't change your mind after ordering that 7.5 frame WBC brood box!) and perishable goods such as flowers and food (ie things with a finite lifespan after despatch). The exact clause is " (c) for the supply of goods made to the consumer's specifications or clearly personalised or which by reason of their nature cannot be returned or are liable to deteriorate or expire rapidly"
There is no actual mention of viable livestock such as bee colonies which one buys with the expectation that the are viable in the long term. So the T&C are again WRONG. So long as you looked after the bees for upto a week after receipt you could justifiably expect them to be fit for transit back in exactly the same way as they were fit for transit in the first place.
However i'd just use sale of goods act which DOES cover livestock and plants. The goods should be: of merchantable quality, properly described
and fit for the purpose. This nuc clearly was none of these.