Dodgy Certificate of Compliance

We bought a new house early in 2001 and a cert of compliance was issued by an engineer and accepted by solicitor. Now selling house and buyers have pulled plans from council only to find substantial differences from our house, room and window layout different as is roof type.

So it looks like the house did not in fact comply and the cert was dodgy. As far as I understand the person who signed off the cert should have made sure he was signing correctly and is at fault here. Has anyone ever come across anything like this before or can anyone offer advice on how to progress? We are at our wits end as retention costs and solicitor costs for probable lost sale will be over 1000 euro which is money we do not have knocking around.

Another point is that the enforcement period is up as it was 5 year back then and the house was completed over 5 years ago. But we are being told that it won't be saleable without retention. is this the case?

Any advice gratefully received.

depends on the purchaser to a great extent but as the 5 year period is up it is easier to sell than during the 5 year period when enforcment could be sought. There is certainty now

AFAIK Certificate of Compliance refers to compliance with Building Regulations, not compliance of build to planning permission issued. If your building is substantially different or if you (or your builder) ignored conditions attached to PP grant, well then retention is in order. I'd guess the buyer's solicitor is correct to insist you get retention PP. Where's the developer? Maybe you have some comeback?