It’s legal!!
According to the lawyers at BALPA it’s legal as long you sign the contract.
There word is that anything in a contract is legal if you sign it and they can take you to court.
I had the same problem and that was the answer I got.
I did not sign the contract
It’s a pain but reality
This is certainly not true under UK contract law, which BALPA advises on. You cannot be held to contract if the terms of the contract have no legitimate place in law in the first place! This is true whether you sign the contract or not.