"Saying that, if my understanding is right then surely Congress should allow the money for his ridiculous wall to be released as it was a campaign promise."
What if his promise was to saw through the continent at the order to cut Mexico adrift; should Congress allow him the money for that?
And remember his campaign promise also included the claim that it would be Mexico, not the US that paid. It's up to him to make good on that part if he wants his wall.
I can, however, see one argument for letting him have his way. In future it could be pointed out as part of mocking future candidates' wilder promises.