For what it's worth, here is my take on things now.
Atlético have reneged on the agreement (which is sound, and proper), but are going to be complicit to forcing through Toby's move to Tottenham. As far as Toby is concerned, I believe that he genuinely holds a lot of fondness for Saints and would gladly sign here, had it worked that way. However, Saints clearly feel that they've been played here, and aren't entirely happy to just roll over and chuck Madrid yet more money.
Toby appears to be at the stage of completing the medical and doing the contract, and signing with Spurs in London sometime this week. If that becomes increasingly protracted, then maybe he is holding out for Saints after all. I don't have any bad blood towards Toby, or for that matter, Tottenham. They would have been just as unaware of the clause in the agreement as the rest of the nation until it was thrown into the spotlight by Saints.
There is of course a chance that Saints could strike a deal that is the same, or better, than Spurs' offer to both the player and the club, but it's fair to say that club relations are pretty much at breaking point between Southampton and Atlético Madrid. Of course, you have to ask the question of whether they'd be willing to go into business with Saints if we could make them a better offer, when things already seem to have progressed fairly rapidly. You also have to question whether Les Reed and the higher powers that be at Saints really want to get down this route if they believe they've acted ethically and with correct morals.
Toby wanted a move to a Premier League club, and he wanted it to be sorted so that he could actually have a good pre-season this year. I don't think he is overly concerned as to which of the two clubs really went for him, as both had their respective plus-points. With Spurs, the Belgian connections and the London lifestyle and potential for a new stadium and regular European football. With Saints, Toby had a squad he knew, a place he had been living for a year and a chance to reunite with Koeman.
As I see it, it looks like Madrid are going to do the deal with Spurs and end up in the courtroom with Saints.
Our anger, frustration and ire should be directly at Atlético, and not Toby Alderweireld, or even Tottenham.
(just my pennies)