Bought A Fish Tank.

Ok, I might do that then, as I think both Cory and neon rasboras need a mature tank. Shame to generate enough bacteria to service a fully stocked tank, then starve them!

You said that nitrite drops to zero but in more than 24 hours. When you get ammonia = zero and nitrite = something under 1ppm in 24 hours, add 2ppm ammonia. Test again in 24 hours.
If both are now zero, the cycle has finished.

If ammonia is zero but nitrite isn't it depends on how high nitrite is. Above 1ppm, do nothing. If it's less than 1, add another 2ppm ammonia. In both cases test again 24 hours later.
This should be repeated, testing every 24 hours and adding ammonia when nitrite is below 1ppm, until you get double zeros in 24 hours after adding ammonia.

If you can't get to the shop for a few days, add 1ppm every other day then do a big water change before you go shopping, either just before or the evening before.

Since you have 0.5 nitrite today, if you have zero tomorrow, add another 2ppm ammonia and if it's zero the next day, then do the water change and get fish. Nitrite must drop to zero within 24 hours of adding a dose of ammonia.

That's the problem with choosing fish. So many species, so little space 

That's fine, just to keep the bacteria ticking over. And that amount won't add much to the nitrate level. 0.5ppm ammonia ends up as just under 2ppm nitrate.

Here they all are!
Swimming happily in my fireplace.

Good choices! I have some CPD myself and think they're great - very characterful little fish. I've also been seriously considering getting some Ember Tetra after seeing some at a lfs recently.

Have been advised they are all male CPD so to try to get some females at some point.

You should be able to sex the CPD's once they've settled in a bit - generally the males have deeper colours on the body and fins but this obviously isn't likely to help if they are all the same! The best way is to look at the anal fin - if it's almost solid coloured red/orange then it'll be male, if it's almost transparent (probably just a bit of colour near the body) then it'll be a female.

I was a bit worried for a while that the shop had only given me 5 CPD or one had gone missing. All six ember tetra had formed a shoal with five CPD.
But I've just counted for the twentieth time and I have six, turns out there's a shy one amongst them!

I think I may have more females than males. There are two I'm confident are male, two fairly certain are female and the other two look more like females to me, but not 100%.
They aren't all swimming close together anymore, but swimming all over the bottom half of the tank.
Btw do female Cpds chase males?

Photo taken just before lights out...

I'd give em a few days to get their colour back - it might not be easy to tell this early on. I do find that the cpd's don't shoal really - they spend a bit of time together but generally like to do their own thing 

Good lookin' tank. I see you're still posting sideways piccies...