Yes, unless you bought in the old part of town. The listed buildings number in the dozens, and most are in the ordinary grade. There's one conservation area, and it covers the historic core. The post-war estates are where extensions happen without much fuss. The heritage rules cover a small corner of Uckfield, and everywhere else is fair game for a loft conversion.
Uckfield has 66 listed buildings: one Grade I, six Grade II* and 59 Grade II. Listing covers the whole building, inside and out, so replacing windows, moving an internal wall or adding a rear extension can all need listed building consent on top of planning permission. Doing the work without consent is a criminal offence, not a paperwork slip. If the house you're viewing is listed, get the listing description and a builder who's worked on listed homes before you start planning an open-plan kitchen.
There's one conservation area, Uckfield itself, which covers the historic centre around Church Street and the High Street. Inside it, the council takes a closer interest in anything visible from the street, including extensions, demolitions, and trees. Some changes that would be automatic on an estate need an application there. Anything a neighbour can see from the pavement should be treated as needing permission until the planning office says otherwise.
The area also has one scheduled monument, the strictest level of heritage protection. It only matters if your land is on it or next to it, and in that case nothing gets dug without national consent.
The neighbours are clearly not put off. Planning records show 2,711 applications across the area between April 2024 and June 2026, including 1,199 in the last twelve months. That's a lot of kitchens, dormers, and garden rooms going through the system, and it's evidence that altering a house here is ordinary, not heroic.
In practice, most Uckfield houses are on estates like Hempstead Fields, Harlands Farm or Manor Park, where permitted development rights can cover modest rear extensions and loft conversions without a full application, depending on the house and whether the rights have been removed. Confirm that with the council for your specific address before you draw up plans. In the conservation area or on a listed building, assume you need consent for almost anything and budget for time as well as money.
Extending in Uckfield is middling in difficulty. On most estates, owners have room to add space, while the historic core and its listed buildings are where plans slow down and costs go up.