Thanks both for your replies so far.
This is why I have the dilema! I don't want to under buy or over buy! If I had the 830 I don't think I'd want to use it as it's so.... sophisticated (?) A bit like having a Ferrari to do the weekly shop in.
Is the 730 still up there at the top top top end or is it still a good enough plodder of a machine to do everyday stuff on but it can be revved up to do exciting things that aren't too daunting for a newbie to full on computorised machines (though not computers).
Is the 640 going to be the opposite once I start playing with the thing and wanting more?
I guess it's the ease of use of the computer screen etc I'm worried about. I don't have a great retentive memory, usually it's full of junk like the next thing I want to make, and reading a manual is usually virtually pointless to me.
Lynn, can I also ask, did you do the course in London or not? London is not the best of places to visit when you're from the back and beyond like me.