U.S. statute is supposedly the same. A valid contract involves consideration from both parties. After you've bought something the contract is set. One party can't subsequently say, "oh in addition you have to agree to this."
Unfortunately law isn't what got written into statute or precedent yesterday. Law is what happens to you in court today.
Please stop talking about "valid contract" or "consideration" here. The EULA almost certainly contains a provision on mandatory binding arbitration.
The validity of the contract may be ignored.
Under "BUCKEYE CHECK CASHING, INC. v. JOHN CARDEGNA, ET AL." and "Rent-A-Center West v. Jackson" mandatory binding arbitration overrides a challenge to the validity of the contract. The arbiter will decide if the contract is valid.
Under "Hall Street Associates, L.L.C. v. Mattel, Inc." the arbiters "manifest disregard of the law" is not enough to overturn an arbitration award against you.
So, no, a valid contract is not required, so long as an otherwise invalid contract contains an mandatory arbitration provision, the "contract" will be decoded by mandatory binding arbitration. If you are a human vs a corporation, your win rate is 0.2% in the national arbitration forum.
A purchase is not required to be locked into a mandatory binding arbitration agreement, because a whether you'd made a purchase would be part of the validity of the contract.
How does one avoid being locked into a mandatory binding arbitration agreement? For example, suppose I run a website that contains a TOS such that it requires visitors to deposit into my bitcoin account scaled by marketcap and a MBAA. When the Google crawler comes by, do I hit the jackpot?
Well, I found this article which seems to present a case where the decision went against the idea of "drive by" mandatory binding arbitration agreements, so I don't think my get rich quick scheme will work.
> There are two types of validity challenges under § 2: "One type challenges specifically the validity of the agreement to arbitrate," and "[t]he other challenges the contract as a whole, either on a ground that directly affects the entire agreement (e.g., the agreement was fraudulently induced), or on the ground that the illegality of one of the contract's provisions renders the whole contract invalid." Buckeye, 546 U.S., at 444, 126 S.Ct. 1204. In a line of cases neither party has asked us to overrule, we held that only the first type of challenge is relevant to a court's determination whether the arbitration agreement at issue is enforceable. [...] But that agreements to arbitrate are severable does not mean that they are unassailable. If a party challenges the validity under § 2 of the precise agreement to arbitrate at issue, the federal court must consider the challenge before ordering compliance with that agreement under § 4.
Could one not attack the agreement to arbitrate on the grounds that no binding agreement could ever have been reached in the circumstances? Even severing the arbitration clause from the remaining of the contract, it seems it could be argued that there was no agreement to arbitration, as there was never any intention to enter into an agreement of any kind (I'm assuming the claimant would argue that they knew the EULA was not valid as a contract and thus ignored the terms). This seems especially so as the FAA specifies "[a] written provision in [...] a contract" - there was never any intention to create a contract by at least one of the parties.
Even if the argument does not hold, framing in such a way would require the courts to consider it (the validity of the agreement to arbitrate) rather than it just passing it directly to the arbitrator.
Perhaps that's just a hopeful reading of the case; it just seems absurd to me as an English lawyer (degree, non-practising) that the arbitration clause can be plucked out and enforced when the contract itself is a farce.
Unfortunately law isn't what got written into statute or precedent yesterday. Law is what happens to you in court today.