Sorry I was being stupid: the HOST_ALIASES line should read:
“HOST_ALIASES=192.168.1.6:22=localhost:2222”
and now it works - I can log into my server from outside.
I would be great if this tunnelling could be incorporated into Thinlinc software so that non-experts such as me could have an easier time 
Anyway - I am now a happy user of ThinLinc