Thanks for all the completed surveys and suggestions; we've hit the limit on the free version of SurveyMonkey! When he gets time (two big tests next week), he will get the results sorted and we will post them here.
All the extra ideas will be noted and used to help the final design. I'm not sure about the precision of the equipment he'll be using, but it is probably better than what I have available, and the DT department staff seem very competent and enthusiastic.
I don't think my son will be going into design, although he enjoys it - he wants to be a civil engineer, preferably on the railways - but I think hifi will be a life-long hobby!
cheers,
Tim