I don't believe the copyright argument will work. Planning Application drawings are public documents and can be viewed and copied by members of the public. Anyway you've been paid for that aspect. When you agreed to seek removal of the planning consent condition, you had a new contract with Builder 1, so it is he who owes you the money. The fact he later lost the plot is not relevant unless he put a clause in to clarify. You could use the County Court process (Small Claims Court) perhaps, depending on what documentation you have regarding the 2nd contractal arrangement.
Its very odd this. Every builder I know takes out an option to purchase land on which he is investing time and money in getting planning. Otherwise he (and his planning consultant) are utilising resources that may increase the value of the land several fold but can lose it at the whim of the landowner - as has now happened.