don't worry, iv found a solution - http://clicksms.co.uk/.
You make an account, buy a minimum of 100 texts (at about 10p each - buying in bulk gets price as low as 5p i think..) and then use a simple php script to send an XML HTTP request to their servers to send the message.
only bad thing is that they don't provide a pre-made sample php script for sending the xml request but i managed to find one on a forum somewhere.
If anybody needs the script id be happy to email (or whatever..) it to them - post in this thread.
(only works with http://clicksms.co.uk/)