The best replacement for o2 is vodafone.

The best alternatives to o2 are rated as following:
★★★★★  vodafone
★★★  o3
★★★  orange
★★★  o
★★  dopod
★★  co2
★  3
★  ee
★  o3 gcc
★  three
★  t mobile
★  magni
★  beyma
★  asgard 2
★  htc
★  c5
★  e12
★  tesco mobile
★  n2 boiling point
★  vodafone 4g
★  e17
★  02
  imate
  tmobile
  cl2
  vali
  ox
  e09k
  be
  n2 have a higher boiling point
  oxygen
  c5d
  sky broadband
  giffgaff
  be broadband
  t-mobile
  orange coverage
  dry o2
  3 network
  i-mate
  carphone warehouse
  wideband o2
  bottlehead crack
  os
  three network
  bt broadband
  vodafone network
  vodaphone
  ipaq
  818pro

Your alternative for o2 is not listed? Suggest!
Speaking about o2, one probably shouldn't forget about free gifts.

Other search terms related to o2 and their ratings are:
★★★★★ free gifts
★★★★★ 3g
★★★ bt openzone
★★★ carphone warehouse
★★★ 4g
★ cpap
★ bipap
odac
topping up
bt wifi
trach
You have in mind a companion for o2 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of o2 in all years. Click on graph for more.
o2
vodafone
o3