NEX6 with kitlens 16/50 *or* NEX6 house with SEL16F28 + WA converter?

It sounds like the 16-50PZ is more what you are after. Especially coming from a P&S. I think you'd be too restricted with just the 12 & 16mm focal lengths. 16mm is usually plenty wide enough for what you are doing and in cases where it isn't, hopefully you can just take several steps back.

Otherwise, consider getting the Sigma 19 & 30mm primes.

I moved to the 5N + 18-55mm + 16mm from a very casual P&S, and spent 6 months with just those kit lenses before buying into other lenses. I personally found legacy manual focus lenses (e.g. Canon FDn 50mm f1.4) a great place to start. Great for slowing down the pace of photography due to MF and incredible depth of field control. I didn't use the 16mm all that much until recently. Now I've got the 12mm adapter since it was on sale and thought it may be fun - but I'd never want that set up as my only option.

I also think you have to consider 'lost cost' when buying new lenses for your set-up. For example, if you were going to spend £300 on a lens, what could you buy instead of that to improve your photography? A tripod, 2 books and a 6 week course at your local college? Will that improve your photography more than a lens? I always try to think about this before buying new gear, and would encourage all P&S upgraders to do the same.

It's annoying really, because I'd really like a Nex 6

All the best in whatever you go with. And just keep it fun