The cast style was done by Rory Kurtz who is on fire in the screen print world right now and him being the artist is what is driving a lot of the demand.
The artwork from The Graduate quad is a piece he originally did for Mondo, I believe. It's very cool, I think. And at the 50 quid mark, which is what the quads seem to be going for, still a bit cheaper than buying one of the Mondo prints...
Well done on the Baby Driver it's a great poster.