People live all over the place and send their kids to Merchant Taylors' schools, there are buses from Southport down through Birkdale, Ainsdale, Freshfield, Formby, Hightown etc. and from Aughton/Parbold/Ormskirk way. If your work's south of Liverpool you might be better off Mossley Hill/Aigburth way, there are buses from there too. Some people live over the river on the Wirral as you can get a train straight over to Waterloo or Blundellsands and Crosby stations, both are about a 10 minute walk from the school.
Formby's alright but in my entirely subjective opinion a bit insular and parochial, it's got a funny mix, as there are lots of middle-class flight types who've moved there for the good state schools, and footballers. It can have a 'we think we're posh' village mentality, Saturday night there is wall-to-wall fake tans, botox and mega boobs plus chardonnay/peroni carnage. Nowt wrong with that of course. Crosby/Blundellsands could be said to be the same, but you can get out more easily!
Southport is quite frankly full of older retired people, and in the summer tourists, so don't expect to get anything done if you're in a rush. It's where people retire to. There are also some quite deprived residents, it can feel like an odd mix between the decayed genteel and the socially/economically disadvantaged.
There are however lots of middle class people too. There are footballers in Birkdale, which also gets a bit Formbyish on a Saturday night.
All of these areas are predominately white, for a more usual mix of people see South Liverpool.
Obviously these are simply my opinions and others are available! 