My understanding of the law is that unless a remedy is stated in the conditions of contract for a breach - which in this case would be working outside the Site working hours (but as you are effectively agreeing to it, by conduct you are altering the Works Information/Scope) - then you are not allowed to deduct your costs.
So unless you come to a commercial agreement outside of the contract as written for the Subcontractor to make a contribution to your supervision costs in order to avoid the higher amounts for missing a stated Key Date, you cannot deduct monies.
So unless you come to a commercial agreement outside of the contract as written for the Subcontractor to make a contribution to your supervision costs in order to avoid the higher amounts for missing a stated Key Date, you cannot deduct monies.