Thanks very much for your response.
My Sat Nav DVD has stopped working. Tested with a copy from my local Audi stealer that confirmed it was a faulty disk as opposed to the unit, however, I am not going to part with Â£200 for another disk. I have 'sourced' a copy, but as it requires a dual layer disk to fit all the data, the default book type on my existing burner i DVD+R (DL) and the device will only work with DVD-R. I have a feeling this has been done to reduce illegal copying rather than the device not understanding DVD+R.
Unfortunately, my HP laptop's built in recorder is an NEC drive with a custom HP firmware, and my other laptop, a Dell, the DVD drive doesn't support changing the book type from DVD+R to DVD-R either. M/N TS-L632H.