Bramblings

Can anyone please tell me how long Bramblings stay in Britain before migrating,  as I still have quite a healthy number feeding in my garden (30 March, 2011). From none three years ago the numbers have grown to up to as many as 12 at one sitting on the feeders. Some have had rings, majority don't. Do they actually stay and nest in Britain? And no, they are definately not Chaffinches. I live in the Lancashire area.