Hey Gary,
We're going to be in the same troop. I had mine a couple of weeks ago, I just got given my joining instructions, so where to go, what to bring, how to be dressed, train ticket issued etc... And we squared away all out standing paper work. I got a free RM Commando pen and thermos mug, *text deleted*.
It's a good chance for you to ask any last min questions you have.
If you as lucky as I was, you may even be asked to give a talk to some lads just before their prmc brief.
As for sizing up each afco is different, so don't be worried if you haven't seen your form yet. I got mine in the post with my provisional date straight after my prmc. It's always a good idea to call your afco though if your unsure as to whether or not you should have recieved that form ready.
Any questions mate just PM me!