The trick with a period property is to stop fighting the bones of the house. Old plaster, timber, original cornicing and big sash windows all have a softness to them — drop a bright, blue-white modern paint into that and it'll look harsh and wrong every time. You want colours that feel like they grew up in the building.
Start with the era. Georgian interiors loved muted greens, stone, soft drab and dusky pinks — Little Greene's National Trust colours and Edward Bulmer's natural paints are built from historic pigment recipes and are hard to beat here. Victorian homes carried richer, deeper tones — think Farrow & Ball Hague Blue, Eating Room Red or Studio Green in a dining room or hallway, where drama suits the period. Edwardian properties soften off again into lighter sages, putties and creams.
For walls that want to read as a gentle off-white rather than stark, Slipper Satin or Pointing from Farrow & Ball are far kinder than a pure white, and Mylands does cracking historic neutrals too. Pair them with a warmer trim — heritage homes traditionally used an off-white or even a soft stone on woodwork, not a brilliant white, so something like Slipper Satin on the skirting keeps it cohesive. Dulux Heritage is a brilliant value route if you want the period feel without the premium price.
The big "but what about" is light. North-facing period rooms can turn a cool grey or green flat and gloomy — lean warmer than you think. Always test big A4-or-bigger samples on more than one wall and live with them for a couple of days through changing light.
Last bit of practical advice: respect the original features. Pick out cornicing, picture rails and panelled doors in a tone or two different from the wall — that's what these houses were designed to do, and it'll look right when a single flat colour never will.