Callum,

Sure, always welcome ;)!

Regarding checking how to use/integrate with your own mechanisms, I would suggest taking a look on the two tutorials we have published a while ago since they are more up to date with latest features  we got in (online CDRs, fraud detection/automatic mitigation, RPC server, various way to control balances and so on).

Here is the link towards the tutorials:
http://cgrates.readthedocs.org/en/latest/tut_freeswitch.html

On the other hand if you want to go with your own development, let me know your particular questions and I can happily share out of what we have learned on the way ;).

DanB