Generally England gets 4 (with the fourth place team going through qualification).
A Europa OR CL champion (not in top 4) would give them a 5th.
A Europa AND CL champion (not in top 4) still gives them 5, but the 4th place in the league would go to Europa next year.
EDIT: I read the original post wrong. A team could never make it into CL by simply placing 5th in the league. Most people usually ask what happens when a team outside of the league qualifiers wins a championship. And that's what I thought the question was. Because it's a relatively new rule that allows for the 5th team. We'll call it the Spuds Exception.