Reporting online crime?

I need to report a possible peadophile, who has started 'grooming' my 9 yr old daughter. He is in ontario, canada, he hasnt as yet said anything sexual, but has said other things that im very very angry as a mother about. I am in the UK, how do I report this man, but keep the conversation with him going so he can say something incriminating. (As soon as I knew he was talking to her, I banned her from the internet and started pretending to be her)