Neighbours giving us grief! Share of freehold

[MademoisellePinot]

We have always been nice to our neighbours but feel really screwed over today and back on the market with two tiny children:
There are 3 of us equal holders of freehold, we are selling our flat and we have accepted an offer from a buyer who wanted to extend the flat in a reasonable way (many other properties have this in the area). The other freeholders have informed the buyer that they will not give consent to an extension (they dont like the idea of noise and that their terrace will temporarily disappear) and our buyer has now pulled out.
how can we ensure they do not withhold consent to either transfer ownership or grant permission to extension to any other prospective buyers? Most people interested wanted to extend...
Another important point is that one of the other freeholders has recently extended their loft in a major way. we didn't sign any permission and the land registry docs have not been changed to reflect the extension.
any advice would be very much appreciated.

You can't stop them objecting - they equally on the freehold. You can offer them something to agree to it though. With the loft, do you jointly own a share of the loft - it sounds like you might if it's a 'share of freehold' deal. You could offer not to take action about that if they accept your buyer's extension

I absolutely agree with the neighbours. You can't usually extend a flat. Is it a converted house or purpose built flat. The other neighbours should not have extended the loft without permission IMHO. I think you need advice from a solicitor re the way forward.

This. You'd have to be a really silly potential buyer to expect to extend a flat.