Hi Tracie two possibilities spring to mind, one a Wren (you can see its tail usually sticking upright), and the other is a Dunnock, they can usually be seen skulking under bushes.
My Flickr photos
In reply to Alan:
Its tail was really small and I'm pretty sure it wasn't stuck up in the air. thanks for replying
In reply to tracie c:
Here is a Wren www.flickr.com/.../album-72157629000058637
And a Dunnock www.flickr.com/.../album-72157629658787997
hummmm I'm not sure hes almost completely round maybe its a baby?