o2.co.uk

Sending text messages with O2 is very easy and has lots of uses:
Whether you’re on a train, in a meeting, or you just can’t talk because it’s too noisy, a text is a handy way to keep in touch.

source: http://www.o2.co.uk/txt/0,,300,00.html

If you want to confirm arrangements, forward a phone number or a reminder but don’t have time to talk, a text is ideal.
It is also useful if someone’s mobile is switched off, as we will send your text to them when it is back on. However we will only keep your message for up to 7 days.

cbfsms.com

CBFSMS.comfrom CardBoardFish allows you to send text messages to any UK mobile phone network for free. SMS

source: http://www.cbfsms.com/

text messaging is both fun and fast growing, so keep in touch with your friends and family quickly and easily using this service. You can even check if your message was received by the recipient using our delivery confirmation system, and check for replies with our free replies system.