Dear JulesI have the hack for the A1.
However, there are about 4 different versions of the firmware depending on when the machine was built. Use the wrong one and the player will die instantly.
The firmware I have is for players built with 2nd edition Denon Link, built after 10/2002.
I can send it to you, but I'd strongly advise you contact Denon for it.
It is extremely risky on a £2000 DVD player.