"Whether we have a legal obligation has yet to be clarified. Unknown, untested waters and all that." - Shaw

Only to you Shaw, only to you.

"If we leave with a walk-away no-deal, with EU nations aggrieved over the non-payment of our dues, trading conditions between the EU and UK will be difficult and there will be obstructive behaviour, even sanctions." - Shaw

If we do indeed leave with a walk away no deal - on behaviour up to now the EU nations will indeed have the right to feel aggrieved at the stance and tactics of Messrs Junckers and Barnier. Trading conditions between the UK and every other country in the world INCLUDING those of the EU will be those practiced under the rules established by the WTO (If the EU fail to comply with this they will find themselves under threat of isolation and "even sanctions").

"We walk away without paying. They won't want to trade."

Really? The German automotive industry will be absolutely delighted when you tell them that Shaw, currently the UK represents 20% of their sales. As usual you present your rather shaky opinions as fact, unfortunately for you your assertions defy the logic and reasoning that the EU sell more to us than they buy from us, so if they don't want to trade with us, who do they sell their goods and products to?

"They may be obstructive. That could include sanctions, de facto or formal."

As Keith A has already said, "obstructive" - No change there, what sanctions that would break WTO rules would the WTO allow?