I did mine with Andy Bridgens and he was thorough. I'd already been riding bikes on & off the road for about 15+ years when I did my CBT though (yeah - took me a while to do me test!).
Was trying to think of anywhere you could go with the bike (assuming you have a mate with a van) to have a trundle around & practise but I can't think.
Big open space that springs to mind is the big rough ground carpark in st johns but it's probably still classed as a public road somehow so you'd need to check beforehand to avoid potential grief.
Even if you only have your own drive/garden/yard etc you can practise starts by starting it, putting in gear and moving a yard or two then rolling it back and doing it again. Better than nothing if you've never ridden a bike before.