Basson's Les Canebiers garden won the international award, planting design and overall best garden award, giving his chances of winning best in show at Chelsea Flower Show 2016 with his L'Occitane garden a boost.
Designer Sarah Eberle, judging the student award, said this year was the first time students were "in control" of their computers when designing, rather than the other way round. Tom Massey won two student awards. He graduated from the London College of Garden Design in July 2015.
John Moreland won the large residential garden and judge's prizes. Judge Richard Sneesby said "hand drawing is important to give designs atmosphere, personality and control" and Moreland's design was "rendered at the end of a 2D pencil". saying his "old school" design's judge's description was "meant as a complement".
One of the founders of the SGD, Robin Williams was awarded the lifetime achievement award.
The SGD Council said: "As a founder member of the SGD, Robin Williams has spearheaded and actively supported ground-breaking work within the Society of Garden Designers to ensure that landscape design is taught and implemented to the highest possible standards and professionalism.
"His design work, which exemplifies this classic attention to detail, has been most generously and humbly shared with students, mentees and members alike. He communicates these timeless qualities of good design in his written works and in the many gardens that have stood the test of time and still delight today."
Other winners included John Wyer for the Lancasters public space, Stuart Craine, Charlotte Rowe, Keith Pocock, Emily Earlam (two), David Loy, Arabella Lennox-Boyd for Eaton Hall, Joanna Midwinter, Juliet Sargeant, Braehead Community Garden and Joe Swift.