Polls: The UNdecideds

The polling numbers are always around 30-34 or something... but that's committed voters.  I want to know what the undecided numbers are.

What are they?

They seem to be the most important numbers if we've known for months that the committed numbers haven't changed.  In the past I always remember the undecided votes to be about 10-15% and that a big hoopla was made when they were at 20%.

I have a feeling that if both Tories and Liberals are stuck at 1/3 each, the undecided number is big.