It depends on which house and which street. The town and its surrounding villages carry 167 listed buildings between them. Nine conservation areas cover specific stretches. One listing is grade one, six are grade two star, and 160 are grade two. Outside those heritage zones the normal rules apply; inside them, the simplest changes start with a form.
The breakdown of the listing register tells you which bracket your house is likely to sit in. There is one grade one listing at the top, six grade two star in the middle bracket, and 160 grade two making up the rest. Listing means any alteration that affects the special interest of the building needs listed-building consent on top of any ordinary planning permission. That captures the obvious things, like an extension, replacement windows, render, roof tiles or internal partitions on a heritage interior, and a much longer list of less obvious ones, including boilers, satellite dishes, the colour of a front door if it sits in a protected sight line, and the choice of pointing mortar. The grade two listings make up the bulk and are the most negotiable in practice, but consent is required regardless of grade, and the conservation officer's notes tend to be detailed.
Nine conservation areas sit inside the wider town footprint. The central stretches cover Upper Bognor Road and Mead Lane, The Steyne and Waterloo Square, Aldwick Road, and the area around the Railway Station. Beyond the centre, the Aldwick conservation area and the Felpham conservation area cover the western and eastern flanks. Out at the village edges, Shripney and Runcton each carry their own boundary. Inside any of those boundaries, the planning rules differ from those on unprotected streets. The kinds of change that would not need an application elsewhere, like external cladding, satellite dishes, certain roof alterations and the loss of distinctive front-elevation features, become applications that have to be submitted and decided. The conservation officer's view carries real weight in those decisions.
In practice, the answer depends entirely on which side of which boundary your house sits. A bungalow on a post-war estate north of the town, with no listing and outside any conservation area, has the same permitted-development rights as a comparable bungalow inland: a rear extension to standard height, a loft conversion, a porch within the size envelope, a side outbuilding within the standard limits, all of these are options without a planning application. A Victorian or Georgian terrace within one of the central conservation stretches, or any of the 167 listed buildings, is a different conversation. The applications go in, the conservation officer reads them, and the answer comes back with conditions attached. The volume of planning work the town processes, about a thousand applications a year across all categories, shows that the system is busy rather than blocked.
The freedom to alter or extend a home in Bognor Regis depends entirely on which side of the heritage line your house sits. On the open estates, the standard rules apply. Inside the listed and conservation zones, those rules belong to the conservation officer, and any project starts with a sketch on their desk.