How can I create a sms number where when people text it they get a automatic reply depending on what they wrote?

Client sends SMS with keyword to short number, Information is stored, looked up in different database, Automatic reply + unique code send to clients mobile based on database . Im in the UK and only need it to work with UK numbers?

I need to know how to do this or which companies can help me. I have a site set up at the moment where some one can email and address with there name and a keyword, this is stored, then an e-mail is sent to them but want them to be able to text a number and a reply sent to there phone… does anyone know where i would start for this or which company i could speak to about implementing this or any information at all… im really stuck!!! thanks in advance =]