OK I think these could be the cheapest in the UK.
www.lordofthedeals.co.uk have Infiniti Samurai 16x DVD-R which I believe are MCC03 RG20 for Â£7.05 per spindle of 25 with free delivery.
They also have Infiniti 16x DVD+R (Not Samurai) for the same price but not sure if they are MCC004. The printables at Â£7.34 also might be MCC004 (If you buy some please confirm on either).
I cannot say for certain if the -R's are definitely MCC03 RG20's but I am going to take a chance and have ordered some. Will let you know. I ordered 100 anyhow.