Mostly yes, as long as your house isn't one of the old ones. About 160 buildings in the area are listed. Almost all are at the most common grade, but listed is still listed. The neighbours put in planning applications all the time. The rules apply one building at a time, not across whole streets.
The Biddenden area has 161 listed buildings: three at Grade I, 11 at Grade II* and 147 at Grade II. Listing covers the whole building, inside and out, not only the front elevation. Most changes to a listed building that affect its character need listed building consent as well as any planning permission, and that includes new windows, knocking through, a rear extension, even replacing the doors. Grade II is the lowest grade, but the rules still apply. Carrying out work without consent is a criminal offence, not a matter of form-filling. If the house you're viewing is one of the 161, assume every idea needs consent until the council tells you otherwise.
None of this has stopped local people from building. From April 2024 to June 2026, the planning records for the area show 3,412 applications, 1,531 of them in the latest twelve months. Local people clearly extend, convert and alter their homes. Many buyers here are planning something from the day the keys change hands.
For the unlisted majority, the position is more relaxed. There is no conservation area recorded across the patch, so the extra restrictions a conservation area would bring don't apply here. An ordinary unlisted house may well be able to do modest work under permitted development, the national rights that allow some extensions without a full planning application. Under 1% of the area falls inside the High Weald Area of Outstanding Natural Beauty, where those rights are tighter. So check whether your address is inside it. Before you buy, confirm three things with Ashford's planning team: whether the house is listed, whether its permitted development rights have been removed by an earlier consent, and whether it sits in that sliver of the High Weald. The seller's surveyor won't check any of this for you.
Freedom to extend here is middling. An unlisted post-war house can be extended with little trouble, while a listed cottage will need consent for almost every change.