HI - there is a one day only deal at the o2 store at the Millennium Dome / O2 Arena today only.
20% off all accessories
20% off all payg mobiles
This is due to the NBA event. If you are near and after a phone etc there are some ok deals to be had. I think it excludes the Iphone (as ever) and a few other bits.
Check o2's website for prices.