Yes, for most houses in Lydney, though a minority come with extra rules. Fifty-odd buildings are listed. There is one conservation area. Neighbours file planning applications at a steady rate. Outside the old core, what limits most extensions is the budget, not the heritage rules.
Historic England lists 54 buildings in Lydney: one at grade I, three at grade II* and 50 at grade II. Listing covers the whole building, inside and out, so almost any change that affects its character needs listed building consent on top of planning permission, including work that would be routine on a house next door. Fifty-four is a small number for a town this size, which means most owners will never deal with the council's heritage officer at all.
There is one conservation area, and it carries the town's name. Inside it, some changes that would need no application elsewhere do need one, usually anything visible from the street, and the council looks harder at how a new extension sits with what's already there. Unless the house is in that area or on the list, the extra controls don't apply.
There is one scheduled monument in the area. That is the strictest protection there is, and it matters mainly to anyone whose land borders it.
Between April 2024 and June 2026, 529 planning applications were made in the area, 220 of them in the last twelve months. That is the most direct evidence that people here do alter their homes, and do it often.
The ground needs more thought than the heritage rules. About 14% of Lydney's postcodes have a recorded mine working nearby, and two postcodes are directly over one. The town was built shipping the Forest's coal and iron out through its harbour, and the workings are still underneath. For any house in those postcodes, order a mining search with the other searches, and expect a lender or insurer to ask for a specialist report if anything turns up, particularly when the plans involve new foundations.
For a house that is not listed and is outside the conservation area, the usual permitted development rights apply. A modest rear extension or loft conversion can often go ahead without a full planning application, though confirm with the council that the rights haven't been removed for that house. In the conservation area, expect more of the work to need an application. On a listed building, assume almost all of it does.
Freedom to extend in Lydney is middling. Most houses can be extended without much trouble, a few dozen are tightly controlled, and in some postcodes the mine workings below matter more than anything planning says.