Mostly yes, unless you've bought one of the old ones. Very few buildings are listed. Five conservation areas cover pockets of the town. The neighbours file planning applications by the thousand. The rules bite here in pockets, not across the whole town.
Burgess Hill has 29 listed buildings: one at Grade I, three at Grade II* and 25 at Grade II. For a town of this size that's a short list, the result of a place that grew mostly after the railway and then again after the war. Listing covers the whole building, inside and out, so any change that affects its character needs listed building consent on top of any planning permission. Grade I and Grade II* are the most tightly protected. Grade II is where most people meet the system, usually over windows they assumed were theirs to change. If your house is on the list, the list gets a say.
There are five conservation areas: Ditchling (The Cottage Homes), Fairfield, Hurst Wickham, Silverdale Road and Birchwood Grove Road, and St John's. Inside them, the council looks harder at anything visible from the street, and some changes that would go ahead without an application elsewhere can need one here. Check with Mid Sussex District Council whether any extra local restrictions apply to your street before you pay an architect to draw something the conservation officer is going to ask about.
The neighbours are not shy about building. There were 2,975 planning applications between April 2024 and June 2026, and 1,322 in the most recent twelve months. That's a town full of people adding rooms, converting lofts and debating whether a garden office counts as a shed. It's evidence that altering a home here is ordinary business, not a heroic struggle. It says nothing about which applications were approved, and anyone quoting a success rate from the volume alone is guessing.
On a typical post-war house outside a conservation area and not listed, some smaller extensions can go ahead under permitted development rights without a full planning application, within size limits set nationally. Flats and listed buildings don't have the same freedom, and conservation areas narrow it. Before starting anything, get a lawful development certificate or a straight answer from the council. It's cheaper than an enforcement notice and a lot less awkward than explaining one to a buyer's solicitor.
Burgess Hill is middling on freedom to extend: easy in most of the town and harder in a few protected pockets. Check which kind of street you're buying on before you start planning the kitchen extension.