Many thanks for that. I've gone for the first one on the list - MistServer. Setup seemed pretty straightforward (I'm running it on a Windows Server 2008 VM). I've got it running, added a user account and enabled RTMP.
I'm now going through the Auto-Configuration wizard on my Windows 10 machine (which will be originating the stream). I've selected the Custom option and entered the URL (rtmp://192.168.4:4242). It starts performing the bandwidth test, but never finishes (it's been running for about 10 minutes now).
Any idea how I can diagnose this?