Yes, for most houses, because most of Billingshurst is too young to be anybody's heritage. A few dozen buildings are listed. There's one conservation area. The neighbours file hundreds of planning applications a year. The planners here are guarding the old buildings, not your late-century semi.
Historic England lists 52 buildings in the Billingshurst area: one at Grade I, two at Grade II* and 49 at Grade II. Listing covers the whole building, inside and out, so almost any change to one of these, from a new window to moving an internal wall, needs listed building consent on top of any planning permission, and doing the work without it is a criminal offence rather than a paperwork slip. If the house you're viewing is on the list, budget for time, specialist builders and a conservation officer who will have views. If it isn't, which describes the overwhelming run of the village's homes, none of this applies to you.
There is one conservation area in the Billingshurst area, named after the village itself. Inside a conservation area, some changes that would be automatic elsewhere need permission, and the council looks harder at anything visible from the street. A council can also withdraw some everyday permitted development rights in a conservation area through a direction, so check whether any such direction covers the address before you plan the extension. Buyers who assume the rules are the same on every street find out otherwise from a letter, usually after the builder has been booked.
The appetite for change is plain from the planning register. The area logged 798 planning applications between January 2024 and June 2026, including 393 in the twelve months to June 2026. That's a steady stream of people adding rooms, converting lofts and changing things they bought and didn't like. The register records the volume, not the outcomes, so it tells you people here try to alter their homes, not how many of them succeed.
In practice, a house outside the conservation area and off the listed register starts with the standard national permitted development rights, which cover many single-storey rear extensions, loft conversions and outbuildings within set size limits. Anything bigger, anything on a listed building and many visible changes inside the conservation area will need an application. Ask the seller for any past permissions or completion certificates, check whether previous extensions have used up some of the permitted allowance, and speak to Horsham District Council's planning team before you commit to a price that assumes the extra bedroom. An estate agent's "potential to extend" is an opinion, not a consent.
Billingshurst gives you an average amount of freedom: easy for most homes, tight for the listed handful and the conservation area. Check which of the two the house falls into before you fall for the loft conversion in your head.