Oh, and in the absence of an edit function to add one more point...
I've looked at the CPS charging guidelines for the Obscene Publications Act, www.cps.gov.uk/legal/l_to_o/obscene_publications/ and it's quite clear that under current guidance the original video, if deemed to have been `published' in the UK, would be potentially actionable:
"activities involving perversion or degradation (such as drinking urine, urination or vomiting on to the body, or excretion or use of excreta)"
However, and it's a big however, it's not at all clear who would be charged, and with what.
The guiding case for Internet pornography is R. v Perrin (www.bailii.org/ew/cases/EWCA/Crim/2002/747.html) which is, by coincidence, a case involving the fetish in question. The accused in that case was actually operating a for-money video service, which although it was hosted abroad was under his control and for his financial gain.
My memory of the original case, which I can't find a reference for, is that the jury found that the stuff that was for sale had an audience small enough, and knowing enough, that it would not corrupt and deprave anyone (ie, buying scat porn means you're already interested in it), whereas the free trailers had a wider audience and may have a corrupting effect. The appeal failed on a variety of grounds, so the basic principle is that in order to corrupt and deprave, a reasonable number of people must be potentially corrupted and depraved.
But this is all moot. The actual video isn't hosted in the UK, nor is anyone in the UK benefiting financially from its sale. So there isn't a `publisher' within jurisdiction. But let's accept, for the moment, that 2G1C is potentially obscene, in that if it were offered for sale in the UK the publisher would be open to prosecution.
But that's not what's happened. LMFM and Coca Cola had a financial interest in the promotion as a whole, but were not making a penny out of anyone who actually went off and obtained the material in question. They weren't hosting it, selling it, getting a royalty on it, and whether MrsR looked and failed to find, looked and found or looked, found and told all her friends (as, one could argue, happened here) is not relevant. Neither LMFM nor Coca Cola are publishers, by any possible interpretation, so that's an end of it.
There are forms of pornography that are illegal to possess or to make copies of, and courts have repeatedly held that the act of downloading something constitutes making a copy. 2G1C isn't such a piece of pornography (no children, and it's not within the scope of the - largely untested - Extreme Pornography legislation). But suppose it were covered. Then people should be careful what they wish for, because in these cases the offence lies in the possession and the downloading. So going to the police and saying "this company encouraged me to download material that is illegal under the Extreme Pornography legislation" is something you should have a lawyer beside you for, because you've just admitted to a serious offence.
As I keep saying, I think what Coca Cola and LMFM did was inexcusable, and they should be held to account in the court of public opinion. Writing, as I have done, to your MP to encourage them to investigate LMFM's dealings with government is a good idea, as is writing to the likes of Tanya Byron (1) to raise it through some of her work. That Coca Cola, Dr Pepper and Lean Mean Fighting Machine all lead to this story when googled for is just, right and proper. It's about objectification, the normalisation of porn, grooming, bullying behaviour by boys towards girls (I use the diminutives advisedly), the sleaze of common discourse, etc, etc. It was a horrible thing for the companies involved to do, and they should pay for it, literally and metaphorically.
However, I don't think an offence was committed, per se, and even if by some tenuous reading of an act you could construct one, I don't think it would be prosecutable. I am not a lawyer, but I've been working in internet law as relating to real world offences for approaching twenty years, to the point of attending Home Office workshops and the like, so I am reasonably confident in my judgement.
(1) I was at a meeting a few years ago with a bunch of MPs and Tanya Byron: like schoolboys when the young French teaching assistant wears a summer dress, I tell you. Mmm, Tanya, how can we agree with you more.