Just remember that on these RHS courses if you get face to face ones , you get the usual PIA professional student who know absolutely everything & has never done anything withbtheir gardening .
Mother nature know best when the plants should arrive and you yourself should develop a feel for your own colour set . Finally Compost just happens ( if you let it )
There's an old saying that, " The bee hives produced honey in spite of the attentions of the beekeeper " .
A similar one is that, " A garden will give up flowers inspite of the gardener , but once they get some success under their finger nails, they will improve moere than a bee keeper " .
Good Luck