Thanks for all the responses.
I don't believe its the media, I feel its a faulty drive.
I was trying to read TDK branded DVD-R media recorded by someone else. Its been making a racket ever since I bought it, though it was working initially. I think perhaps it may have been damaged in transit and then normal use has sealed its fate.
I've had to go back to my Sony DRU530A which doesn't bitset for DVD+R :sad: