Right, when I made the colony I right clicked on the system view and 'create colony' did not appear, I clicked it a few times just to make sure. That I suspect could be the problem here.
Then I sent a Xeno team to investigate, at least I think I did as they never got there. Can't say for sure that I correctly set the team up there though.
The 2nd time I set a team up they showed as present on Proxima Centauri A-II on the population-teams tab and after a few months reported back on the events log that they had discovered a ruined city.
Sadly, this has not been reflected on the summary page and I don't know what else to do. I've left the xeno team there for the time being but I suspect that my there is something wrong with the db.
Apart from the fact that it has taken something like 30 years and more than 10,000 crew lives to get this system I would leave it but after all the heartache I want some sort of reward at the end.