Doubt everyone can help you.

You can easily see how many are currently listening to Caroline North on their own Shoutcast server page. Currently around 315.

But there is another big chunk of RCN listeners (around 50% ?) using Manx AM's stream. I don't think these numbers are available to the general public since the server stats are hidden. Peter Moore may know or have access. So few outside the organisation will have the complete information you are seeking.

I enjoyed hearing Ron Brown and miss him from Atlantis UK since they dropped all presenters.