Thanks for all the welcomes and advice.
Araucana16, that sounds like a really good idea and exactly what I'm going to go ahead and do.
Yesterday I went out and got some more hens - I bought a beautiful Buff Orpington hen, which laid an egg shortly after I got her home, 2 Potchefstroem Koekoek hens and 6 Leghorn chicks, a few days old.
The hens are all together now and the roosters have been separated for the time being.
The Australorp hen seems to have been appointed 'top hen' and her and the Orpington hen have made it their duty to look after the chicks - so sweet to watch!
I'm also getting a silkie hen today.
How does that work with the silkies - i'm assuming they are more broody and as such are used to incubate any fertile eggs?
Yesterday I collected my first eggs!

One from the Australorp, the other from the Orpington.
What a sense of satisfaction it brings!
And they just seem to taste so much better when you've had a hand in it.
So the plan for now is get as many hens as I can and then after a while introduce the roosters.
I they still don't get on I'll separate them into 2 flocks, one rooster each - one for the garden and the other for a coop I'm building