It is a couple of years since I went through this and things may have changed but this is how it worked for me.
Went to court - issues outlined by both parties very briefly in front of a judge and a CAFCASS officer then each of us had a separate audience with the CAFCASS officer which in my ex's case took half an hour and with me about 10 minutes. I believe that sometimes this meeting is done with both parents but I think in our situation, it was recognised that any agreement at that stage was beyond hope. CAFCASS officer talks with judge and then we were called back in - judge made interim order for contact/residence and ordered a report based on the concerns I had raised.
Report was supposed to take 16 weeks - ordered 1st April and finally received on 14th January the next year! In meantime, we were in court a couple of times for CAFCASS to explain themselves. Once the report was received, the ex agreed to a
Consent Order without it going to a final hearing.
I had three interviews with CAFCASs - the first officer essentially abandonned the case (was sacked), so really it was two. I had no telephone contact with them. Paperwork was sent out following the first court hearing asking for details of doctors, health visitors, schools etc. and for permission to contact them. They were all contacted and produced written reports - not all of these were attached to the final CAFCASS report I assume because they said nothing at all of any consequence either in my favour or the ex's. Interviews took about an hour and was quite general. I had taken extensive notes with me about what I wanted to cover so I didn't forget anything. It is worth saying that the second Officer refused to look at any of my back-up info - emails, phone conversation transcripts etc. saying it was procedure that she only looked at what was put before the court. The first officer went through everything - I have no idea who was right/wrong but it was very disappointing with the second one! If I were going to do it again, I would take a list of specific questions/queries and read them from the paper so I know they've been asked - one of the issues for me was the girlfriend hitting our children which, if the report is anything to go by, was entirely overlooked (I suspect I am about to end up back in court over this issue some 2 years later).
Our children were seen in both homes and the eldest was spoken to in school -by which point he obviously had seen the woman a couple of times so was familiar with her.
It was pretty painless, really. I was listened to but I'm not sure I was ever really heard and the recommended outcome was the standard one - residence with mum, dad to have every other weekend, one day during the week and half of all holidays (he had wanted 50/50). Of course, as soon as the ex had his piece of paper, he did just what he wanted! but that's another story!