theeksource.com is pretty decent, but it's becoming a bit out of date now. For the 2-class ER's i've been doing similar to what RichL was doing, but looking at the Glasgow route, before it changed to 3-class. For the 3-class ER's, i've been going by theeksource and looking at data.flight24.com and seeing if any of the aircraft listed as the old seats have been out of service for more than a couple of weeks. Not the most accurate ways of looking at it, but it seems to work. Not entirely sure about the 3-class aircraft, some that I have listed may have been refurbished, but there is definitely no more than what I have listed. Hope this makes sense!