Yes. For most houses in Hatfield Peverel, an extension faces only the standard planning rules. There is no conservation area. A few buildings are listed, and one ancient monument nearby is protected. The clay underneath is the main thing to plan around.
Hatfield Peverel has 22 listed buildings: none at Grade I, 3 at Grade II* and 19 at Grade II. Listing protects the whole building, inside and out, so changes to a listed house need listed building consent as well as any planning permission. That covers walls, windows and staircases, as well as anything added to the back. If you own one of those 22, every change goes through the council's conservation officer. If you own one of the hundreds of unlisted houses around them, the conservation officer has no say.
The area also has 1 scheduled monument, the strictest level of protection. Hatfield Priory is the scheduled monument here. It mainly matters for land next to it.
The planning records covering the area logged 2,215 applications between April 2024 and June 2026, and 1,008 in the last twelve months alone. So people here do change their homes, often. With that many applications, the planners have almost certainly seen something like your plan before.
The ground needs more care than the planners. The British Geological Survey puts the area in shrink-swell class 3, and 100% of the area reaches that class. Shrink-swell clay expands when wet and shrinks when dry, so foundations for an extension usually need to go deeper. Trees near the new walls matter too. A structural engineer and building control will set the depth, and that cost should be in the budget from the start. The clay is the one constraint here that applies to every house.
Without a conservation area, an unlisted house generally keeps its permitted development rights, so many single-storey rear extensions, loft conversions and outbuildings can go ahead without a full planning application, within the national size limits. Flats don't have the same rights, and listed buildings need consent whatever the size of the change. Check whether the house is on the national list, and whether the planning permission for its estate removed permitted development rights. Braintree District Council can confirm both.
This is a good place to buy if you want to extend. Planning restrictions are light, there is no conservation area, and the deep foundations the clay needs are the main extra cost.