I have hired from four yards in my time on the broads and one in Scotland. The one in Scotland, Maffetts and Freedom were excellent. They are assessing your ability and knowledge as they take you out. I have no doubt if you show you are not ready they will carry on showing you, indeed that is what Maffetts said they do. HW was back in the mid 80's and was very poor, so not really relevant today. Richardsons seem to have a set trial, down the river, turn round, stern moor and off. I think they do a side moor if you have not been before. Not sure what they do if you have not displayed competence.
i have been on boats quite a bit and always plan and read up well in advance. I think the real problem is the people that give no thought to what can go wrong. It does not mean that they are bad people it is just they way they are. The yards need to recognise this and educate.