Plumbing problem in new build but 2 months out of warranty

[cakebaby]

Developers warranty ran out 2 months ago, we've discovered a problem with the central heating cylinder which will be repaired under a policy I took out with British Gas. However during diagnosis it was discovered that the installation was faulty in that the waste overflow pipe was not connected, resulting in a small flood can using damage to the ceiling downstairs. To connect it means ripping out part of the ceiling then making good the damage. Contacted the installation company, they're not interested as out of warranty, same with the developer. I'm pressing for one of them to take responsibility as the installation was incorrect, we just didn't discover it in time, there was no way we could have known. Does anyone have any advice about how I should proceed please? Would trading standards assist or NHBC?

Have you got it in writing from British gas that it's an installation fault? If you have, send a copy with an attached letter to the company who originally installed it. You can threaten them with trading standards but, think it might be a case for the small claims court unfortunately.

Gah! More bother. Thanks for your reply though

Watch, 'the sheriff's are coming' that is on BBC 1. It has lots of good advice that might help you.

Thank you, developer is now taking an interest once I get a report from British gas.