Yes, in the sense that yes is technically achievable, but the process is closer to a negotiation than to construction. Brighton contains 1,376 listed buildings. Thirty of them are Grade I, and eighty-four are Grade II starred. Forty-four conservation areas cover much of the city. The consent stack is what people are actually complaining about.
Listing is the top of the constraint pile. Brighton has 1,376 listed buildings, of which 30 are Grade I, 84 are Grade II starred and the remaining 1,262 are Grade II. If a home is listed at any grade, changes to its external appearance and much of its internal fabric require listed building consent from the council, and that consent is separate from and additional to any planning permission. Windows, doors, chimneys, roof coverings, internal walls, floorboards, staircases and fireplaces can all fall inside the listing envelope, and swapping any of them for something modern typically triggers an objection. The Grade I entries, which include the Royal Pavilion, are effectively frozen at whatever state the last approved change left them in. Grade II starred is only slightly more flexible. Grade II, which is where most of the count sits, is where the negotiation actually happens.
Conservation areas are the layer above the listing. There are 44 of them across the city, and they cover much of the Regency terraces, the Georgian squares, the Victorian streets radiating out from the town centre and several of the outer wards. Inside a conservation area, some of the permitted development rights that would otherwise let a homeowner extend or alter without a planning application are removed, particularly for cladding, painting, satellite dishes, front-facing extensions and boundary walls. The council can add further directions that switch off more permitted development rights on specific streets. A homeowner who has bought without checking which directions cover their address will find out at the point of applying to build.
The practical position is this. If the home is a modern build on an unlisted plot outside a conservation area, standard permitted development applies and a rear extension of the ordinary size is straightforward. If the home is a Victorian terrace inside a conservation area on a listed street, the sash windows are non-negotiable, the render colour has to match the neighbours, and the rear extension needs planning consent even where a permitted development elsewhere would not. Between those two positions is where most Brighton homes actually sit, and the answer to almost any specific alteration is check first. The council's conservation officers will look at drawings before they are formally submitted, and that is the cheapest way to find out whether the plan is buildable. Assuming permitted development on any pre-war street inside Brighton is a category error.
The freedom-to-alter score is one out of five, which is the lowest tier available. That is the price of owning a home in a city that has decided to look like itself in perpetuity, and the price is not going down. Anyone who wanted a garden studio, a rear extension and modern glazing without a two-year consent process should have looked further inland, where the map is not covered in hatching.