Right, I have a 120 litre (3ft) tank with 8 phantom Tetras, 4 Hi-fin Platys & a small Bristlenose plec (4-5 inch). Would I be ok to buy say 6-8 neon Tetras as well or is it fully stocked now?
Yes, that would probably fully stock the tank (it's a good idea not to surpass the "inch guideline" during your first two years of fishkeeping if you are a beginner.) Neons should not be introduced to a tank younger than 6 months. (ie. 6 months since water was first put in the tank.) WD