Yes, for most houses in Downley an extension is a realistic plan. Very few homes are listed. There is one conservation area. The neighbours file planning applications as a matter of routine. The rules tighten around the common and the edges, and loosen everywhere else.
Downley has 18 listed buildings, every one of them Grade II, with none at Grade I or Grade II*. Grade II is the commonest grade of listing, and it still means listed building consent for most changes that affect the building's character, inside as well as out, alongside any planning permission. For a village of family houses largely built after the war, 18 is a short list, and the odds that the house on a shortlist is one of them are low.
There is one conservation area, Downley Common. Inside it, the council takes a closer interest in changes that alter how a house looks from the street, and some work that would be routine elsewhere needs permission. The Le De Spencers Arms at the top of the common was once a bakery, and these days that kind of change on the common comes with paperwork. About 12% of the area also falls inside the Chilterns Area of Outstanding Natural Beauty, where the rules on what can be built without an application are tighter than on an ordinary estate. Buckinghamshire Council's own maps show whether a particular house falls inside either boundary, and that is the line on the map worth checking for any address on a shortlist.
The planning register shows people are getting on with it. There were 975 applications logged for the area around Downley between April 2024 and June 2026, with 400 of them in the last twelve months. That is a lot of extensions, loft conversions and new windows being argued over, and it is decent evidence that alterations here are normal.
For most of Downley's post-war semis and detached houses, outside the conservation area and the Chilterns boundary, a modest rear extension or loft conversion may fall under permitted development and need no planning application at all, subject to the national size limits. Inside Downley Common, or on a listed building, expect to apply, and expect the council to look closely. The same plan can be a weekend's paperwork on a close below the common and a long correspondence at the top of it.
Downley gives most owners a fair amount of freedom to extend and alter, with the real constraints confined to the common, its handful of listed buildings and the edge of the Chilterns. Buyers who want room to grow will find more of it here than the village's age might suggest.