Excellent replies, thanks people. Its funny to hear it's almost common for babies to grow up in there.
The tank is a fairly new one, set up in July, it was second hand but arrived dry and spent a couple of weeks in the living room before I got the new lights and filters all set up. Everything that went in it was moved across from a 180l tank so I thought id seen literally everything there was to see so I was pretty surprised get my hand bumped by it when I was cleaning out the filter box!
It must have come from the shop is a tiny fry mixed in with one of the other cichlids. Its great, and so well coloured for such a young fish. I think shes big enough to evade her tank mates now so fingers crossed I'll see more of her, maybe I'll get her a mate!
Thanks again
Dan