NEC ECSC: ownership and title to construction work

We are contracted under a NEC short form sub contract to complete civil works for a main contractor who in turn is under NEC option A with a large client.
We have completed works and left site with all snagging works completed and are now experiencing severe problems being paid for our last 2 valuations which are overdue by 8 weeks and 4 weeks past the due dates.
The main contractor will not engage with ourselves to discuss this issue.

Are we able to approach the Client and claim payment from them instead
If the client is not able to make payment to ourselves or withhold payment from the main contractor until we are paid who legally owns the works we have completed and what can we do to enforce our claim to the building and works until we are paid.

The main contractor would still have high value mechanical and electrical works with testing and commissioning to complete and claim payment from the client.

You can approach the end client and ask for payment, but they have no obligation to pay you as they are not in contract with you.

The short contract is a bit skimpy on title so the position defaults to the common law position, namely that once Plant & Materials are incorporated into the works, the Client owns them. So if you were to go back and remove them, you would be stealing.

The first thing to do is keep on submitting your application before each assessment date. Add interest due because of the late payment to each application. A lack of response as to why they should pay you less plays into your hands. It is then a fairly simple adjudication to get a court order to be paid: the dispute is not over the amount unpaid; it is that they clearly have not followed the procedures in the contract and the Housing Acts so owe you the money claimed (whether that amount is right or wrong).