6059 was the vehicle involved in that accident at Low Fell where a cyclist was killed whilst on N21 duties. As far as I know that's the only accident involving an angel.
I also think you won't have to worry about the Diamond Mercs because the only other one they've done was the Citylink I think (I think they were bought new for that, you'll probably know

As for Presidents;
6019 and 6022 have spent all of their time with GNE at Chester I believe as they were purchased new for the 21 in 2011, although I think 6026 has been somewhere else, maybe Winlaton (once again, your the one to ask).
Here is 6008's obituary;
Bought Mid 2011 for The Angel from London General? (I can't remember which company, maybe Go Ahead London, I don't follow any movements outside of the company, I just stick to them while with GNE, I'm afraid I don't stalk them.
Debranded when the Hybrids arrived and sent to Stanley October 2012
Transferred to Deptford last week.
To be continued...