Recommend any free email to sms service

[hwarden]

I need to build a client website which will allow enquiries via a contact form on their website. They wish to receive SMS alerts whenever a customer completes their booking form.

I would like to know if there are any free services that I can use. My client is based in the UK so the system you recommend should ideally be able to send SMS on any given UK network.

You can also suggest any paid solutions that don't cost a fortune?

Thanks