Yes, and Chandler's Ford is one of the more straightforward places in Hampshire to do it. The town is barely touched by heritage protection. There are eleven listed buildings across the whole area, no conservation area covering the built-up part of town, and a single scheduled monument. For a homeowner weighing up a rear extension or a loft conversion, that near-absence of protected fabric is the whole ballgame. Most houses here answer to the ordinary planning rules rather than the special ones reserved for old and precious buildings.
The listed-building count tells you why. Eleven is a small number for a town of this size, and every one of them sits at grade two, the base level of listing rather than the exceptional grades reserved for the genuinely rare. That does not make those eleven easy to alter. If you happen to own one, changes to the fabric need listed-building consent on top of anything else, and the rules bite hard on the details that give the building its character. The saving grace is arithmetic: with only eleven listed buildings in the whole area, the odds that the house you are buying is one of them are slim. This is a town largely built in the second half of the twentieth century, and modern estate housing does not attract listing.
In practice that means the average Chandler's Ford homeowner is working inside the normal system, where a fair amount of ordinary alteration falls under permitted development and can proceed without a full planning application, while larger or more visible work still needs consent from the council. Permitted development is not a blank cheque, and it does not apply to every house or every project, so the honest first step is always to check your specific property rather than assume. What the wider picture suggests is a town where altering a home is routine rather than rare: roughly 960 planning applications went in across the area in the past year, which is not the profile of a place where the council reflexively says no. People here extend, convert and reshape their houses, and the paperwork is a hurdle rather than a wall.
The blunt verdict is that your freedom to extend or alter a home in Chandler's Ford is well above average. Unless you have bought one of the eleven listed buildings, the past is not going to stand between you and a bigger kitchen. Check the property, follow the process, and get on with it. This is a town that lets you change your house, and that is worth more than most buyers realise until the moment they want a second bathroom.