Martin, be extremely careful about this one. We get it on almost every job in the insurance claim side of things, and we always use a Mandate to protect ourselves, didn’t realise you would get the same, obvious really I guess.
Technically you should only work under the instruction of those who will pay you or those as appointed to give you instruction on their behalf; however you are entitled of proof of that.
The LA's agreement or clause with their client is nothing to do with you and therefore the ex tenant should receive copy of your estimated costs and sign to agree them including any payment conditions before work starts.
Alternatively the LA can issue you an official order, which they will be very used to doing, no doubt with their terms of payment on. And that’s the only way you should really work otherwise you can and will get caught, only a matter of time.
You can of course produce a condition whereby the LA has the provision to instruct you, providing the client pays you within 14 days otherwise the LA becomes responsible for the full bill. This is a derivative of the Mandates we use, which have been tested in court on a number of occasions.
On this particular point I’m happy to fax you a copy to adapt, or I can post out, just let me know.
On this job, Natalie is absolutely right, continue to invoice the LA if they back up on you, advise them that you can send a copy of the invoice to the client but that’s all.
Unless you have seen sight of any agreement from the client in respect of these works, you made your contract with the LA unless he told you that you would be invoicing the client before the works started, in which case you would have technically agreed "bad move if you did".
DP.