Hello SerpentWanderer,
You sound like you are on the right track, but i'll throw out some tips anyway
The main thing is to ditch the gravel, if your snake swallows it by any chance, it can lead to impaction and death, since it can't be passed by small snakes. Gravel is also not absorbent and hard to clean, so whenever your snake defecates, which would be once a week to once a fortnight depending on the snake, all the gravel will have to be removed and washed. I would suggest newspaper, cat litter (the paper pellet kind) or my personal favorite, Kritters Crumble, it comes in a big bag and lasts quite a long time. It is also very absorbent and if your snake swallows some it's not a huge deal.
That being said, depending on the size of the snake, I would just use paper towel or newspaper to be on the safe side until it's larger. BUT this all depends on whether you are going to feed it in the tank.
Are you planning on housing it in the one enclosure it's whole life? If so I would just bump it up too a 900mm enclosure, (assuming the 600 meant mm lol), maybe not necessary with pygmy pythons, but for a spotted or a children's I would.
Also concerning the electrical, the UVB isn't necessary, not for a python anyway. A normal light is fine, if you would like to save some money.
I don't know too much about fan heaters, but I'm assuming they heat the air?
You'll need a focused basking spot for the snake, not just warm air, also a heat gradient. A heat lamp works well, as would a ceramic heat emitter.
Lastly, I cannot recommend this enough, but there are several great books that will help you along the way.
"The complete children's python" By Justin Julander, Nick Mutton, and Peter Birch. (while it is specifically for children's pythons i'm guessing 99% of the information can be generalized to the rest of the Antaresia species)
"Keeping and breeding Australian pythons" By Mike Swan (I have this one and it has alot of general python/reptile keeping info, as well as specfic species info)
"Guide to Australian pythons in captivity" By Adam Elliott
Hope this helped you out, feel free to ask more questions