Just thought i would give a bit of info about these incase anybody didn't know about them, as i find them extremely useful. You have to be on o2 PAYG.
For o2 numbers, you pay £5 every month, and you get 1000 minutes or texts to use to the 10 numbers that you pick. It does say that it can only be for o2 numbers, but i use it with numbers that are on t-mobile etc and it works just as well. This is an outstanding offer, a fiver for something that would normally cost £100. You can change numbers every 30 days and i use this aswell as my free 300 texts everytime i top up - leaving me with 1000 texts to my 10 numbers, 300 to any other numbers, and £5 credit, all for just a tenner.
O2 bluebook is useful for a couple of reasons for me, its free. It automatically saves every text you send or receive online, so you can view them at any time. This is handy incase you have important texts or lose your phone etc. I also find it good for uploading pictures. You can take a picture with your phone, and then send it (for free) to the o2 number, and it will then save that online aswell, which you can then save to your pc from there. Saves hassle of cables or bluetooth especially if you are not able to.
Anyway just a bit of info for you there i thought it might be useful for anyone on o2 who didnt know about them - sorry if its in the wrong section or something