I haven't seen this on here, and it's a freebie so i thought I would give it a go incase somebody gets use out of it!
On the o2 website, go to (send free text message) and you will be asked to register, you will then be able to use the 10 free texts every month, that's 10 free texts, which can be sent to any uk mobile, and it's free, it's pretty self explanatory, but it does explain itself it much better detail on the site so read if you want to! (it's o2 so you don't get any spam text messages or anything like that)
As far as i know it works with any network (for example if you are on orange, you can still register your mobile number on the o2 website to recive the free txts)
It's probably not the best deal in the world, but texting off this o2 website is much easier, faster, and safer than using other free SMS web services
Be gentle as I am unsure as to how you guys will respond to this deal... but... it's a freebie, it's handy, and it's not a virus or spam... so should be ok