Thank you. You have a contract to do a job for a price. You are entitled to be paid the contract price for doing the job. If they decide that they are going to get some jobs done elsewhere perhaps cheaper, whether they are using your own contractors or not, then you are still entitled to damages in respect of the loss of profit for the work which they are now having done by other people.
You have a further remedy in respect of the contractors because there was an agreement for them to do this work for you and it is now being done directly by them and hence, you have a claim against them in respect of the profit that you would have made on the work that they did and in respect of your markup.
In essence, your claim against the contractor and the customer is in respect of however much you lose in profit as a result of their actions.
Ignoring the architect for a moment if it was agreed that the customer would pay you at the end of each month and the only reason he is not paying you is because the architect hasn’t signed the certificate, then whether your claim against the customer for late payment would succeed would depend on whether that late payment was contractually dependent on the architect signing.
If it’s not, and they are just habitually late payers, then you can add interest at 8% simple onto the amount you, from the date it became you under the provisions of the Late Payment of Commercial Debts (Interest) Act and a fixed sum of £50 upwards under the provisions of the Late Payment of Commercial Debts Regulations on each invoice if it’s not paid on the date due. The amount of the fixed payment depends on the value of the invoice. Here is an explanatory leaflet:
Can I clarify anything for you?
Please don’t forget to rate the service positive. It’s an important part of the process by which experts get paid.