That's fine Andy, so long as the cake arrives in the first place and is serviceable (in this case edible).
Paper plates, no frills, fine... that's what I expect for 50p but I wouldn't expect to be told on arrival in the bakery... "yes, we received your order and took your money, but there's no cake available and what do you expect? You only paid 50p... durrr!"
No brainer really.
We don't expect frills but there IS an obligation on any supplier to deliver the goods as promised or come up with a vaild excuse why that's not the case and make necessary recompense.