Ah, that's good to know.
I'd already allowed ufw through port 8333 but hadn't forwarded the port in my router. I've done that now and currently have 11 connections, so I must be running in full node mode.
That would be correct. One thing I would add is you can limit the number of connections ( maxconnections=n in either the config file or on command line). The default is 125. Understand however you can only set a limit, the number of peers that actually connect to you will vary depending on how many peers need outgoing connections, how many addressable peers exist, and how reliable other peers see you (in terms of uptime). It is very likely that you will not reach the max connections but that is actually a good thing, it means there is "spare capacity" for outbound only nodes.