Got a longer seat post last week (thanks to those who suggested that) so I can now set the saddle at the same height as I’m used to on a bike. It’s made a big difference - I was out at the weekend practicing on some tarmac and I found it much easier to put weight on the saddle than when the seat was a bit low. Also my arm flailing is almost cured (balance seems easier with the saddle higher as well) and I can now freemount almost every time (yay!). So now I can officially claim to be a “level one” unicyclist 
The freemount in my tutorial book is the “start with pedal at the bottom then kick back with other foot before riding off” method, and I found that extremely hard, so I’m using the static mount method, which seems much easier and, as I said, I can now pull this off almost every time.
Turning smoothly (by leaning rather than by twisting the body in sudden swerves) is still a bit wobbly and needs more practice (especially to the left for some reason), then I’ll have a go a idling…
Rob