"Now all of this is run of the mill stuff for your friends solicitor to include in the contract."
I am sorry to disagree, but it isn't. The norm in the sale of new houses is that the contracts are drawn up by the Builders solicitors, and they are usually very slow to allow any changes.
It is also the norm for a builder to supply a floor area certificate, but it has never been normal practice for the supply of the certificate to be a standard contractual obligation. It can become a contractual obligation depending on what is laid out in the 'Booklet of Title' documents which usually accompany the contracts for the sale of a new house, but it is not contained in the standard Law Society contract.
It could be argued that this is a gap in the standard terms and conditions of sale, and no doubt the Conveyancing Committee of the Law Society will take a look at this sometime with a view to beefing up the standard conditions. The reality here is that the law in this area has changed several times in the past few years, and it is difficult for solicitors to keep abreast of all the changes.
The house was only recently bought. For all we know, the buyers solicitor spotted the issue and raised it immediately, only to be told 'take it or leave it'. What more would you have this solicitor do?