Yes, and in most of Yarnton the rules are the ordinary ones. The listed buildings are few and clustered. No conservation area covers the village. People apply for planning permission here all the time. The clay under the garden will have more say over your extension than the planning officer does.
Yarnton has 28 listed buildings: one at Grade I, two at Grade II* and 25 at Grade II. Listing covers the whole building, inside and out, and any alteration that affects its character needs listed building consent from Cherwell District Council on top of any planning permission, including changes that would otherwise need no permission at all. Grade I and Grade II* are the top tiers and get the closest scrutiny. For the other homes in a village of post-war semis and bungalows, 28 is a small number, and the realistic question is whether the house you are viewing is one of the 28. The Historic England list answers that by address in a minute or so.
The planning records hold 973 applications for the area between April 2024 and June 2026, and 422 in the latest twelve months. That counts what people asked for, and nothing more. It does say how normal the idea of altering a house is around here. Whatever you are planning, a neighbour has probably drawn it, submitted it and talked about it over the fence already. The council's online planning register will show any past applications on the house you are looking at, including the conservatory the last owner swore was approved.
The ground is where the real conditions are. The British Geological Survey rates shrink-swell potential, the tendency of clay soils to swell when wet and shrink when dry, at class 3 across all of Yarnton. That is a published hazard class and moves no house on its own. What it does mean is that an extension here may need deeper foundations than on firmer ground, and a structural engineer will want to know what is under the footprint and which trees are nearby before signing off a design. The paperwork is easy here. The digging takes longer.
For most homes, that leaves the standard route. With no conservation area in the village, ordinary houses keep the normal permitted development rights, which cover many single-storey rear extensions, loft conversions and outbuildings within national size limits, sometimes with a prior-approval step and sometimes with nothing to submit at all. Anything larger, anything on a listed building, and anything on a property where those rights have been removed by an earlier permission goes through a full application. Building regulations apply either way, and on clay they will be the part that costs.
Freedom to extend is one of Yarnton's real strengths. A handful of listed buildings take all the heritage scrutiny, and everyone else just has to dig deeper.