Ah yes, sorry! I did include SVP in my research ... I have used them a number of times before, and I just forgot to add it in my list :). I didn't include the Ritek G05 discs as they only burn at 8X with release (2.18) firmware and are more expensive than disks that burn at 16X with release firmware.
As for Prodiscs03, whilst they are cheap they only burn at 4X with default firmware.
Prices are higher here than in the US, but unfortunately that is the way with a lot of things. I guess you don't pay Â£3.60p ($6.78) for a gallon of fuel
If anyone has any better deals on DVD media in the UK that burn at 12X or above with release firmware, then please post here!
The table below may assist:
CMC MAG. AM1+
CMC MAG M01