Topic: I think I'm finally learning something!
This is part-celebration and part-thank you to all those people who have helped me with far too many questions over the past month or so. I think your help is actually getting somewhere.
I have three times today opened a "New Thread" post and started writing long explanations of my problems and each time I have thought to myself "hang on, maybe I could do it this way". Each time I have got myself a little closer to the planned end result: a rather complicated (in my opinion) "new resource" page with two polymorphic sides to it - one of with is a many-to-many relationship - using multi-selects and radio buttons and on-change. I'm sure the code is horribly inefficient and untidy at the moment but right now I don't care. It works with minimal outside help!
I'm so chuffed that I've managed to get this page working, in just under three hours, without help. But I also realise that if it weren't for the help I've had previously on the boards (my post count is getting horribly high considering I'm unable to help anyone else yet!) I wouldn't have managed it! So thanks to everyone who has (and probably will in the future) helped me with my multitude of silly problems!