Hi Tony, I know what you're thinking but the songs you have on your videos are either not covered by copyright or they are covered by copyright and youtube already know about them. You may think you have disguised them but I would have thought that youtube will have found them in a few minutes of you posting them.
To check this go on the youtube and find one of your videos with music like the 'Anglesey Ribnet Cruise August 2011' video, when it starts to play look under the bottom right hand corner and you will see the artist, song name and a link to itunes to buy the song.... I believe this means you have been allowed copyright to use the music with your video on youtube.
If you then go to the top righthand side of your screen and if you are logged in you will see your user name and a drop down menu. Go to this and select 'Video Manager' you will then see a list of your videos and the copyright information and the restriction each video has, for example it may have been allowed copyright worldwide except Germany.
However, as far as I am aware there is no list of music available to say if it's going to be ok or not, so you don't find out until you upload it. So when you have chosen a tune and imported it from itunes just slap an unedited movie on it and then upload. Within a few hours it will either mute because the owner of the copyright has not given youtube permission for you to use it, or you have got permission and it's linked to itunes so the artist could get a sale or maybe a bit of commission from the advert they will now show when your video is played via the youtube website.....
Once your happy with all this, delete the video from youtube, go back to imovie and then work your magic.
If you want loads of hits on youtube, just call your video 'Charlie bit my finger' and you will have a million hits by Christmas
The above is how I understand it, so please correct me if I'm wrong.