PhdLife, you should definitely go for it if you can find the time to put it together. Competition for fellowships can be tough, but you only stand a chance if you actually put in an application. And if you have a great idea, that may be the edge you need over people who have more papers.
Having applied for a fellowship myself recently, I would say you need to allow as much time as possible, and use everyone you know to look over it and comment. See if your grants application department have some successful applications to look over (fellowships are similar to other grants, althoug there tends to be more emphasis on personal development). Contact the funding people directly with any questions you have. And if you know any obvious people in your field who might be asked to review your application, MAKE SURE YOU REFERENCE THEIR WORK!!
Even if you don't get it, it's a really worthwhile experience - it forces you to focus your ideas, and think about what you want to do and how, it makes you much better at the process next time round, and I think it enhances your CV - not as much as getting one, of course, but as a demonstration that you're serious about applying for funding for your work (rather than just talking about it) and that you're aware of the process and the requirements.
If you really don't have the time at the moment, then I sympathise, but don't just write it off as a passing whim - it could have longer term benefits. Even if you don't make this deadline, you could write up your proposal anyway, and keep an eye out for other funding calls it might fit into.
Of course, I'm never one to take my own advice - I have an idea sitting around that keep meaning to write up properly as a proposal but haven't got round to yet...