I've been having a think about this, and although i've only just bought a Williams 2, i think the 2's are just for people who want a cheap Williams (in the main anyway, maybe not EVERYONE!).
I've based this on the original Williams being the "original", ie, it was the first edition, and the one which started the great reputation, so thats gotta be a good one to have. But if you wanted a newer Williams, and one with more electic gadgets, you would buy a Williams 3 because of the sunroof.
So, why would anyone want a 2, unless thats all they could afford!? Unless of course it was an outstandingly mint low mileage example or something
This could be interesting............ or i could just get a rather big slating!