Received pronunciation is so named because it was 'received by', i.e. taught to public school pupils and RADA pupils.  ( RADA = Royal Academy of Dramatic Arts ).  You can hear example in most British movies made before about 1960.  Most notably, in black and white WWII movies, there are two nain categories of accent: officers and men.  The higher the rank, the more likely the actor is to be using received pronunciation.

The term 'received pronunciation' was first used, I believe, by the phonetician Daniel Jones.

As for 'mid-atlantic' pronunciation, this is also best observed in films.  British actors would learn the American accent and American actors would learn received pronunciation.  I would suggest that when these actors travelled and mingled they formed, from a linguist's perspective, a language community.  When two languages or dialects come together, they move towards a common centre.  So, from England and America, the common center idea of the accent is taken almost literally by placing it in the middle of the Atlantic.

I hope this is of help to EFL students.

Patrick Lockerby

Orson Welles as Lamont Cranston in his radio performance on the "Shadow" series used mid atlantic, one of the most beautiful I have heard.

Jim Backus as Thurston Howell III lampooned mid-atlantic in Gilligan's Island"

Franklin Roosevelt had a very thick mid atlantic.

Walter Chronkite used mid western standard.

Seth MacFarland  has the best AND funniest received pronunciation from a non native  as Stewie in "Family Guy.