Good news indeed - I'm happy to beta test having a DVD R/RW drive at hand.
You write "2.4x writing might be possible on a RiscPC". I doubt that that speed will be possible on a Risc PC. I did manage to burn CDs on my ex-Risc PC with 12x using a Blitz IDE for the harddisc and an Eesox SCSI for the bruner. When I told Steffen that that worked he was very surprised of the speed my setup managed and first couldn't quite believe it- and that was just 150 x 12 x 12 = 3600 kb/sec!
If you have a CD ROM R/W drive and want to burn DVDs I'm afraid that you will have to get a piece of hardware: A DVD bruning drive.