Was in Sainsburys today, and all Verb's are half price. Yes I know, not exactly cheap but not bad if you don't want to pay for shipping.
50pk CDR Â£6.99 (MII)
100pk CDR Â£10.99 (MII)
50pk DVD +/- R Â£8.49 (MIJ)
25pk DVD +/- R Â£5.99 (MII/MIT)
They also had 25pk RW's but I can't remember the price.