Yes, and the planners are the least of your worries. No conservation area covers the village. Only a handful of buildings are listed, and none of them are grand. The catch is underground. In Lyneham you can build more or less what you like, but the clay decides how deep the foundations go.
Lyneham has 15 listed buildings, all of them Grade II. There are no Grade I buildings and none at Grade II*. Listing means consent is needed for almost any change that affects the building's character, inside or out, including the kind of work that would otherwise sail through. With only 15 listed buildings in the whole village, the odds that yours is one of them are low, and the conveyancing searches will tell you if it is. There is no conservation area inside the boundary. Bradenstoke and Hilmarton each have one nearby, so check which side of that line a house sits on if you're looking beyond the village itself.
The neighbours clearly aren't put off. The planning register logged 1,017 applications between April 2024 and June 2026, including 469 in the last twelve months. Those figures record applications, not what happened to them, so they say nothing about how many were approved. What they do show is that people here alter their homes regularly and expect to keep doing so. Each application also leaves a public record, so looking up what was proposed next door is the best free research a buyer can do before a viewing.
The ground needs more care. The British Geological Survey puts every postcode in the village in class 3 for shrink-swell, its published hazard rating for clay soils that swell when wet and shrink when dry. That's no reason to cancel the extension. It is a reason to budget for a structural engineer's view before the architect gets carried away. Clay like this can mean deeper foundations than a builder's first quote assumes, and it affects where the trees can stay. The surveyor who spots hairline cracks around an existing extension isn't being fussy. They're reading the soil.
For most homes, the post-war semis and terraces that make up the village, the ordinary rules apply. Plenty of rear extensions, loft conversions and outbuildings can go ahead under permitted development without a full application, as long as they stay within the national size limits. Listed buildings lose most of those rights, and some estates have had them removed by condition when they were built. Check the planning history of the specific house, and if in doubt, ask the council for a lawful development certificate before a builder starts digging. It costs far less than a retrospective application.
Lyneham leaves homeowners a lot of freedom to extend. The heritage rules barely apply, so the main things to plan around are the clay and the foundations.