A good few years ago a friend had a Jetranger and after taking off he was in the hover and said I am going to let you have some control. I took the collective and the cyclic, he covered the pedals and said after ten minutes I was a natural.... So I suppose it could be done in twenty minutes to assess if someone is capable of going further. Not sure it helped either that I was a fixed wing PPL (well in the hover that is). Sadly I am probably too old now to take up any offer. I have to add, I have been to Northumbria Helicopters and on first apperance looks very professional