Today I looked at the RSPB Willow Warbler page and my heart sank because I couldn't find the Listen' link on the left-hand side. However, I thought it would be very surprising if they had removed the bird song altogether, so persevered and cursored through the page listening to every line and found a greatly improved listen immediately below the picture of the bird. It's 01:58 minutes long. I have my little recorder all ready to take with me to the Forest tomorrow, when my brother comes to visit, so have recorded it; firstly to make sure I know the song well, and secondly to play it in various areas, in hopes that an anxious WW will sing to challenge!
The more I listen to it, the more I think I have almost certainly heard a WW during the last few years, but have mistaken it for a Chaffinch song, sung by a bird who's forgotten to put the 'per-CHOO' flourish at the end of his song!
Dave-at-the-gym has suggested a good spot for easy access and a place where I should hear others - he's written me a list of 6 or so- woodland birds. At least the weather is going to be just right it seems.