The general advice holds across all three: if the specific bank holiday date matters, book as early as the diary allows; if flexibility exists, the days immediately either side usually offer a similar break with an easier drive and a calmer park.
The practical case starts with the beaches themselves. A stretch of sand near a park like ours on the Yorkshire coast staycations or East Anglian coast that's genuinely difficult to find space on in July is, by late September, wide open. Rock pools, dunes and the tideline are easier to wander round at leisure, without weaving between other groups, and a dog can be let off the lead on stretches that carry summer restrictions.
For a couple, a short break, two or three nights, usually built around a weekend, does most of what's needed. There's no school-term constraint to work around, less packing, and less need to fill every day with an activity. A Friday-to-Sunday trip to the coast gives a proper change of scene, a couple of decent walks, an evening meal out, and time to properly switch off from work without using much annual leave at all. The travel time matters more here than for a longer trip: somewhere within two hours' drive makes the most of a short window, since a five-hour round trip eats into what's a fairly brief stay to begin with.
Term-time also shapes what's worth doing once you arrive. Crazy golf courses, amusement arcades and seaside cafes near a park like ours run full hours through the school holiday weeks and cut back once term resumes, so a trip planned around half-term rather than a random week in September gets the full run of what's open. Check opening times for the specific attraction you have in mind before you travel, since some seasonal cafes and smaller museums close earlier once the summer crowds thin out.
Booking early is less about beating a queue and more about choice. A pitch with a sea view, a caravan that sleeps six comfortably, or a week that lines up with both parents' annual leave: these are the bookings that get taken months out, not the week before. Parks along the English coast, ours included, tend to open the following year's summer diary not long after the current season closes, so the families who book in autumn get first pick of the following July and August.
Booked around October half-term or simply a quiet weekend before winter properly sets in, an autumn coastal break trades the crowd and the guaranteed sunshine of August for space, colour and a slower pace that plenty of regular summer visitors never see.