I don't think it is dead to be honest, there just aren't any political organisations that are suitable for promoting it in this day and age. Organisation always lags behind political consciousness, it took 50-60 years from the Chartist movement and the slow development of Trade Unions until we had a Labour party, and it might take decades for new organisations to emerge too.
What holds back the UK radical left, and I include trots anarcho's and etc in this, is that the organisations we have are the relics from the ideological battles of the 20th century, ones that the left almost uniformally lost. There's still plenty of left-wing sentiment about, and infact more now than there was only a few years ago, but there's no way to take that sentiment and make a practical impact on politics because of types of organisations that are around.
I also think there's a historical context, because since 1984 the left's been on a roll of defeats, and that's led to deep cynicism setting in, something you'll find plenty of evidence of on these boards. With a few exceptions, poll tax springs to mind, there's been no victories on the left for a very long time. We need a victory, even just a small one, to turn this tide. You never know, I have a feeling that all it would take is one strike to be victorious, to pick a random example, and it might lead to momentum gathering.
Every few years the left has some big demo or march, or even things like the student protests and so on, and I don't think I'd be alone in saying at those times there's often a sincere mood of optimism that follows it, like when we do have a big march and we feel the strength of our numbers it does wonders, and invariably after this that momentum gets squandered. Like after the students trashed millbank, there was genuine excitement, coz for the first time since the government got in there was a palpable sense of panic, and it had an effect on everyone I know.
A final point I wanna make, just coz I'm young enough to have noticed it, is that speaking to people who are like 15-18, just leaving school or college kind of age, they're noticeable more politcally aware and sympathetic than kids of my generation who grew up under Blair. My little brother's mates are all college age, and whenever they come round the house or I see 'em out and about they're always asking me questions about the economy, about why there's no jobs. That's a change that's worth mentioning.