Painswick doesn't quite make the list mainly because of its conditioning. I reckon there are a few small windows to play Painswick. In the spring before the rough can grow and in the fall after the rough can be cut and before the mud sets in.
I think Kington is also the best of these courses. It is a proper design with some cool shaping and unusual fairway undulations. Perranporth is probably better than Cavendish just because its on sand and the course is easily played all year, but in terms of the design Cavendish knocks P'porth all over the room and because of this I place it 2nd. Cavendish certainly suffers from drainage issues, even so, I greatly admire the design and think it is an excellent model of where architecture should be heading. I like Painswick, but it is very extreme; a game once or twice is year is enough for me whereas if Cavendish was that close to me I would consider joining and if Kington were that close I would have been a member these past dozen years. I reckon Painswick's par 3s really make the design (one of the best and most varied sets I know of), but there are also a few wonderful 4s highlighted by some terrific green sites. Other than for safety issues here and there, nothing should change and all should see Painswick at least twice
It truly is a marvel.
BTW - I don't really think Perranporth is a hidden gem. It is quite a popular holiday course.
I know you aren't a Dealie in the same way some others are, but I am surprised Deal isn't among your top 25. Whats the problem?