A nice idea, and I'm open to correction, but I don't think Charles Church ever took his Spitfire in to Popham; IIRC he was operating out of Blackbushe. I can only recall one late mark Spitfire (MkXVI?)occasionally visiting, and also Peter Vacher's superb Hurricane. Oh and a (kit-built) Spitfire Mk26 that I enjoyed a back-seat ride in, if that counts!
Popham fly-in days ... all I can suggest, apart from a good read of the website (which you have clearly already done) is to listen out on frequency early to get the active runway and circuit clear in your mind and to assess other inbound traffic, join overhead, keep a very good lookout, be prepared for a go-around ... and either get there early or arrive in the lunch-time lull ! Also on the microlight trade fair days, if the weather is good, my personal view is ... arrive by car!