I know that you are aiming this survey at rescues, but there seem to be so many buns floating around just now.
My first came from a friend, whose husband was planning to release it in the woods. I said we would have it because although I didn't know anything about rabbits knew it was the wrong thing to do.
Second came from SSPCA, was a baby born in the rescue.
Third came from SSPCA, Dundee, was left abandoned at rescue with another rabbit.
Fourth, I have just adopted after finding him hopping around our road. He has weepy eye and I reckon he has been dumped.
For the future, it would be a good idea to contact all the rescues that are on here or connected. Set up a central area with a recording area for each rescue so they can record this data for future. If it was done along the lines of an excel worksheet for each named Rescue, you could link those worksheets onto a total sheet and then have all the data at your fingertips, maybe not for this year but for future years.