So, some further news.

At the planning committee meeting on Nov 20 as reported previously they voted to overturn the refusal - actually because of procedure, now its recommended for grant its open again to objections. So it had to be deferred till this months meeting on Dec 18 for vote for formal grant. Anyway, the Chairman opened the issue and reminded the committee what was previously agreed and without further ado asked for a show of hands; it was unanimously agreed . but then the planning officer piped up "we haven't discussed any conditions". At which point the legal officer said "You've voted, so you can't add conditions afterwards". So we have permission to build a generic side and rear extension, rear dormer and general external alterations with nothing to stop us as regard size, materials, etc., since there's no condition that says we have to conform to the approved drawings. Serves them right! Of course we won't be taking too much advantage of this...