No advice for the airports. Been to all except PLS, just even if you get the "right" side, you may be on the wrong side if the wind changes and you come in on a different runway.

Main advice: Who are you flying with and have you enrolled in an Airline Programme? The folks here will be able to advise the best programme(s) to maximise your miles.

LHR-PLS direct suggests this is a Oneworld Ticket. You may be able to work an AA Challenge.