Re: Its pass the book time.
While you may be able to make a claim for a fault for up to six years, unfortunately that won't really help (other than in a vanishingly small number of cases).
That's because, broadly speaking, up to six months the assumption is that the fault was present at time of purchase. After six months, the onus is more usually on the buyer to show that there was an inherent fault. And "not being compatible with the actions of a third party, which couldn't have been forseen at the time of sale" would not, I think, be what anyone could consider an inherent fault.
Fit for purpose is a slightly different matter, but even that is unlikely to extend beyond a limited time, sufficient for trying a piece of equipment and establishing whether or not it works. You can't retrospectively apply it. Otherwise, for instance, anyone who bought an analogue only TV set would be able to make a claim because of digital switchover. Or, for example, if you bought a set with a CAM so you could watch TopUpTV when it launched, only for that service to be discontinued, you wouldn't expect to be able to get your money back for the TV then, would you?
I would imagine that the only situation in which you might possibly have a small chance of a claim would be if you happened to buy one of these sets very recently (ie, probably within the last six month, so you don't have to prove an inherent fault) and you made clear at the time of purchase that watching YouTube was a key factor in choosing that set. Since the affected sets are older models, the chances of that are pretty slim.
Yes, it's pretty crappy behaviour on the part of manufacturers not to do updates for older sets - my first gen Panasonic VieraLink will doubtless fall foul of this - but I can't see any way in which the switching off of a service by Google could be turned into a claim under SOGA or other consumer regulations, so long after the sets were sold.