CAP 712 was withdrawn some time ago. It was quite a confusing document & development of SMS has moved on.
If you search around the UK CAA website there is/was a document entitled SMS - Guidance to Operators, which last time I checked was at Version 2 October 2008. I think this replaced CAP712.
Also available is CAP 726 Auditing SMS. This is a ccontains a checklist based on the CAA SMS roadshows conducted in Autumn of 2008, which I have used and then reproduced in an audit report. It's quite a good tool for identifying initial gap analysis.