Eggshell is the right call for the vast majority of homes. It gives you a low-sheen, slightly soft finish that hides imperfections in older timber, wipes clean when the hoover bashes it, and sits comfortably with modern matt walls. Full gloss is a relic — it's hard-wearing, yes, but it's shiny, it shows every dent and brush mark, and it dates a room instantly.
For a proper trim eggshell, Little Greene Intelligent Eggshell is excellent — water-based, tough, low odour, and it self-levels beautifully. Farrow & Ball Modern Eggshell is another cracking option with a slightly flatter sheen (around 20%) that pairs perfectly with their matt emulsions. If you want a touch more durability and sheen, Dulux Heritage Eggshell or a satinwood from Crown will give you a harder-wearing surface for high-traffic hallways.
The big "but what about" question: should skirting match the walls or go white? Both work. Painting skirting the same colour as the wall (in eggshell) makes a room feel taller and calmer — very current. If you want crisp contrast, a soft off-white like Farrow & Ball Pointing or Farrow & Ball Slipper Satin beats brilliant white every time; pure brilliant white looks cold against any decent wall colour.
A word on prep. If your existing skirting is old oil-based gloss, don't just slap water-based eggshell over it — it'll peel. Give it a proper sand to break the sheen, then prime with Zinsser BIN or a good adhesion primer before your topcoat. New or bare timber wants a knotting solution on any knots, then a wood primer.
Two coats of eggshell, light sand between, and you're sorted. Skip the gloss — eggshell is the smarter, better-looking, easier-to-maintain finish.