Hey Kristy, I have no experience at an urgent transition but I was going to suggest a couple of things.
Sometimes a toddler bed just isn't viable for lots of reasons. DD is an amazon child and was almost too long for the cot at just over 12 months old. A Toddler bed uses the same mattress so for us that just wasn't a usable option.
I think the single bed is a great idea, and two things helped with my two (who went in at 16 and 11 months respectively), either just trial him on the mattress on the floor (with or without a bedrail - some kids need it for a sense of security, not just to prevent them falling out), or take the castors off the ensemble (if that's what you choose) so it isn't so high.
Good luck, but don't worry. He'll probably surprise you.