You certainly do have to wonder why OCUK don't automatically refund. Is there some breach of contract legal thing going on, with OCUK being the ones that would be in breach on contract if they fail to supply the contracted goods?
I be surprised if that was the case, there is stories of other stores failing to fulfil stating reasons outside of their control, but it might be a unknown if a judge would deem a alternate SKU with similar specs as been a suitable replacement so maybe they dont want to chance it. Your thought is a interesting one.