I'll just give a boatload of info here...
-The park's maximum capacity is around 15,000. They can officially hold more, but there's internal H&S/operational considerations they go with. A "sold out" day will probably have around 14,000-15,000 people, as a buffer and also as some pre-booked guests don't turn up.
--There's some caveats to this. A "sold out" day may have less people if they have ride closures, expecting certain types of guests, etc. Buy out days are obviously capped at less.
-The quietest days I've known of have been less than 1,000. Very rare, but has happened. Last time I think that happened was like 8-10 years ago, when the park was open for a full week after FN. Those weekdays were dead.
-These days, September weekdays are probably the quietest. You're probably looking at around a couple of thousand people. Even then, that will vary quite a lot day to day. The park can still feel quiet if there's 2,000 people on park or 4,000 people on park.
-A standard weekend day will again vary significantly, likely around the 5,000-10,000 mark.
-A "busy" day, in terms of how the park feels and copes, will likely be anything above 9,000 I'd say.
It's an interesting situation that the park are in. 10-15 years ago, their weekends / "peak" days were heaving, and their off-peak days were dead. Like 10,000 might he standard on a weekend, and 1,000 on a weekday. The park wanted to increase attendance by increasing attendance on those quieter days.
They have of course managed to increase attendance on quieter days, but it seems to be that people are choosing to visit on those days over busier days, as opposed to attracting more guests. That helps on an operational standpoint in that the park can plan more consistent staff levels. But it now means that the park, and staff, are less used to busier days.
As I say, back in 2012, for example, 10,000 on a Saturday was normal and the park coped fine. These days, 10,000 on a Saturday is abnormal, in that it is more than usual. So that means the park doesn't operate as well, and it feels worse.
It also means that when we hit those capacity days, it can hit even harder.
I guess the big takeaway is that Thorpe, and indeed basically every theme park in the UK aside from Towers, hit small arena / stadium numbers. For a football example, we're looking at like League One/Two football matxh attendances (which are weekly things) on a daily basis.