It's completely, totally and utterly irrelevant what the law in this country does or does not say when it comes to towing a toad on an A-frame in Spain. It is also irrelevant what the DfT says, what European law says and indeed what Spanish law says. The fact is that people get stopped by the police, fined and made to decouple. Isn't that the only knowledge that is relevant? It's then up to each person what they do or do not do about it.
Eventual results of the poll associated with this thread will be interesting: