I got the same text message yesterday (11th July 2011). Having heard about scam texts, I didn't try to do anything with it, just ignored it. I'm going to call 3 about it now.
OK, so I've just phoned 3 and was assured that this is not a scam and if I send a STOP text to 33777 I will not be charged. I have just sent the text and received one back saying:-
"FREEMSG: You are now unsubscribed from Free Stuff, you can subscribe again at any time by visiting the Free Stuff page on Plant 3. Stop request processed."
TV on Demand is part of the 3 service, so it all seems genuine.
When I called 3, Anand in the call center said it was not one of their numbers. Tried to send stop again about 5 minutes ago but same response number " NOT ALLOWED "
What number did you use Tricia ?