Your final stock is a good start. I recommend at least 6 black neons: it's not fair to keep schooling fish in small groups and you don't have any excuse for not doing so.
Can i get anymore in there? (using a tt 1200 external and a u2 internal) need to add these in slowly tho hey. I have lost one of my new neon's that i purchased this weekend at lfs tonight

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just done a test and Ammonia is 0.50 time for a water change
That ammonia is painfully high, it would also explain why the neon died and others probably will too before long. Have you not cycled the filter? Or had a problem? For the sake of the fish, keep that ammonia (and nitrite) as close to 0 ppm as possible, and never let it reach 0.25 ppm.
You should not be considering any more fish right at this moment and wait at least 2-3 weeks after your filter is cycled before thinking about adding more fish. I can't tell you what your tank will take in total, but it's a fair assumption that it will take more fish. I recommend you get all the schooling species up to 6 fish per species first, then consider the top-ups. By that time, you should be able to tell if your tank can take more fish or not.