Procurement method for sub-sub-contractors

We typically engage as a (reasonable sized) sub-contractor under NEC3/4 ECS, and occasionally JCT SBC.

Our method of procurement is usually by way of purchase order or similar, historically we have never really engaged with a supplier or sub-sub-contractor under any form of NEC or JCT contract.

We have experienced of recent some time related issues with suppliers whereby we have been unable to recover any delay damages/LADs as any terms applied to us via the main contractor have not been applied in our procurement method with our sub-sub-contractor.

Would anyone be happy to propose a suitable method (perhaps engage any large/time related sub-sub-contract packages under NEC ECSS) or wording that carries the same terms as that of our main contract?