Looking at the map
It already borders housing estates and in a decade or two it would probably be built over anyway. If the Tories had any nous about this, they would have zoned it industrial, got businesses to build on it, then offered them very generous incentives to move "elsewhere".
If it is going to be concreted over anyway, I'd rather we ease the congestion on the largest/busiest International airport in the world... With the constant noise abatement regulations on jet engines, the noise pollution actually goes down. We don't have Concorde any more, we don't allow jets which are not bypass (damned noisy, just try standing around a south American local airport), things keep getting reduced over time.
You can be in Paddington in 20 minutes from Heathrow, contrast 50 minutes for Stansted, 45 minutes (best if you don't have to wait for the transfer bus), for Luton and 30 minutes from Gatwick after you have trailed to the train station which is not in the terminal.
Personally I would have preferred the new airport in the Thames Estuary favoured by Boris. This would have been the UK leading the world, doing something new, getting new opportunities. However it would have cost 5 times as much, required a whole new transport link and some environmentalists would have complained about the "stress" on the local wildlife... Funnily enough environmentalists never seem to realise that wildlife adapts faster than humans do.