I don't think any of DD1's classmates were flown in to take the entrance exam! Most of them live closer to the school than she does (we are in Exeter).
There might be an issue with the Maynard if that is the case, certainly people who don't get into Colyton do get in there but they might find it pressured.
The kids and teachers I know at Exeter school seem less pressured, similarly with St Margarets. You might want to consider Blundells as well? Again, less pressured. But that is a boarding school.
St Margarets is the easiest to get into of the Big 3 posh schools (unless you are a boy in which case obviously there is only the one option) but the results of all 3 schools are pretty comparable. None of the kids I know who go to those 3 schools right now own ponies. :)
It really is a minefield choosing a school in Exeter/Devon, there is such variation. The illusion of choice can be disorienting. But, I know kids who have been to the big 3, several of the local state schools, QE in Crediton, Colyton, Bramdean (a sort of second tier posh school in Exeter) Stover and Blundells and they have all, without exception, gone on to good universities, and then to have good careers and happy lives. The schools here are actually all pretty good for conscientious kids. The amount of choice we parents have is bewildering but I find it comforting to think that at the end of the day, the kids seem to be doing just fine even in the face of all our worries.