Does anyone know of a website that allows you to send free text messages to users of o2 cellphone network? I know that there are Polish websites that allow you to send sms's to PLUS GSM or HEYAH for example.
I spent a lot of time looking this stuff up because I needed it for a website I worked on that had to send out text messages - basically you are after an "SMS gateway service".
Unfortunately in the UK the mobile companies don't offer this service. I am sure they did 10 years ago but it seems that they don't now. There are services and websites that you can use but you have to pay to send messages. Have a google for SMS gateway and you will find a few of them I am sure.
There are quite a few providers who will let you send 'free' SMS messages. One category will make the recipient pay (eg Yahoo) and another where they will attache annoying marketing crap to the messages (loads of these).