Thanks for you replies.
I have checked the water quality on a regular basis and it is fine. The tank was second hand and the gravel had be kept wet, as had the sponges in the filter so I would like to think that this has helped it establish quite quickly. Previously to me having the tank it had been running for about 3 years. I have also been adding some of the old water from my other tank which has been established about 4 years everytime I have done a water change. (about twice now as i have got baby guppies in that one).
I think I may return the Danios to my smaller guppy tank, as I would like to have some larger fish in my new one. I was going to add 3 or 4 Gold Gourami's in the future once it has matured some more. My kids are also crazing me to get a couple of Angel fish, but I think they will soon gobble up the neons and I wouldn't want that
How much longer do you think I should leave the tank before adding anymore fish