Yes, for most houses. About 519 buildings across the area carry a listing. Thirteen conservation areas overlap the town and its villages. Ten scheduled monuments sit inside the same footprint. Which puts Littlehampton in the higher-than-average bracket for heritage constraint, where extensions and alterations meet a consent gate more often than in a coastal town without the same historic fabric.
On the listed side, around 519 buildings in the wider area carry a formal listing, made up of 12 at grade I, 16 at grade II, and 491 at grade II. Listing at any grade means that changes to the building's fabric, its windows, its roof line, and often its interior features cannot be made without listed building consent from the local council, on top of any planning consent that a change of size or shape would separately require. Grade I and grade II apply the highest bar. Grade II is the working majority and the one most residential buyers actually deal with. The listed stock is spread across the wider area rather than concentrated in a single quarter, so whether a specific property is affected depends on where in the area it sits and what the building is.
On conservation areas, Littlehampton and its neighbouring villages sit inside a network of 13 designated areas. Three cover parts of Littlehampton itself: the seafront, River Road, and East Street. The rest cover villages including Angmering, Lyminster, Warningcamp, Poling, and Burpham and Wepham. Conservation-area status does not stop you extending a house, but it changes what is possible without formal planning consent. Categories of work that would ordinarily fall under permitted development, such as changes to windows, external cladding, roofing materials, or the removal of trees, can require full consent inside a designated area. The local authority can also apply directions that further tighten what an owner can do without applying, so what worked next door may not work at your address.
For a typical Littlehampton house outside a conservation area and not listed, the standard permitted development rules apply. That means single-storey rear extensions within the size caps, most loft conversions, and a range of front and side works can proceed without a full planning application. Bring the same house inside a conservation area, and several of those routes narrow. Bring the same house into a listed building envelope, and the routes narrow again, with the added requirement that any change respects the historic fabric of what is being altered. The practical advice for buyers is that no serious extension plan should be committed to before a check with the local planning department on the specific address, and no purchase should be committed to on the basis of what a neighbour on a similar-looking street got approved.
On the freedom to extend or alter a house then, Littlehampton scores below the typical town for its scale. Not because you cannot extend anything here, but because a higher-than-usual share of houses run into a consent gate of some sort before the works can start, and the buyer who assumes otherwise is the buyer who finds out late.