BBC2's Working Lunch program just had an interesting piece on mistakes and misprices.
It was about credit cards actually, but certainly has relevance to recent discussions on misprices and the recent Dixons fiasco.
Referring to case law and the 'Doctrine of Mistakes' they quoted the Argos TV deal a while back and the Kodak one. Basically the conclusion was that where the mistake was obvious ie. Argos advertising a TV for £2.99, not £299, then the supplier can break the contract without repercussions, as no-one would expect to get a TV for £2.99. Where Kodak where concerned, they advertised the camera at £100 instead of £300. They had to honour the contracts because it wasn't unreasonable for consumers to expect to get a camera for £100, even though it was cheap.
On this basis any legal action against Dixons won't get anywhere as a 40" TV for a £1 isn't ever going to be considered likely so the fact that Dixons confirmed the sale and took money doesn't help. Amazon would have been on dodgier ground with the recent Ipod offer, on this basis. Perhaps this is why the £20 vouchers were issued.
You can view the programme on the Working Lunch site if you have Broadband, I believe. Hope this is helpful.