After careful thought I have decided to continue with 1-1 training.
Wise choice IMO.
Pete 
When I did my HGV training, back in the days when you could go straight from car licence to c+e in one go, I shared the training with another person.
I actually think this helped, for a start spending all day driving and learning is tiring and because you are concentrating on driving and what’s happening at that moment you don’t have time to analyise things.
I found I got on with my driving struggling with certain parts, but then when the other guy was driving I had a chance to think about what I’d done and watch what was going on and analyise it and think about how to tackle the situation without having to concentrate on driving as well.
I actually think this helped, for a start spending all day driving and learning is tiring
You may well be correct. But this is why 1:1 training is normally conducted in shorter sessions.
Pete