AusBonsai

at first i thought it was flower petals ( a tiny brown dot, with a tear drop shaped white thing attached) slowly more white stuff (1mm) underside of melaleuca leaves. Then fluffy white thing between stem and leaf (2/3mm), i scraped a few with a tiny wire, the white stuff came away revealing a tiny skin coloured thing even on the paper bark I don't know why? but the little trunk has even gone blackish, like after a bush fire

I'd say you nave some sort of insect sucking the sap out of your tree. There are a couple that make white woolly covers to protect themselves from predators. Woolly aphid is one but there's also mealy bug and I recently saw another one with a tall white hat- quite cute but still sucking sap out of the leaves.
There's a lot of them on this tree, all sucking sap so the tree must be feeling quite ill. If it is not already looking sick it soon will.
The black on the trunk is called sooty mould. It is a direct result of the bugs on the leaves. As they eat the sap they excrete sugary liquid. If the ants don't take it all it falls onto the leaves and trunk and sooty mould grows.

Get rid of the woolly buggers and you'll stop the sooty mould (though the black that's already there won't disappear until the bark peels)
Soapy water can deter most of these bugs but you'll need to do it several times a week until they all go. Non toxic but more work for you.
Pyrethrum is low toxicity insecticide that can kill most sap suckers but it is a contact insecticide. It will only kill the ones it touches so you will need to spray really thoroughly several times.
Systemic insecticides travel right through the plant and will kill any insect that bites the plant. They do a good job but there may be unintended collateral damage to non target insects like bees. Confidor and Bug Killa are systemic insecticides but you'll need to go to an independent nursery. Bunnings don't stock these any more.

I get those on my Callistemons all the time. Generally I'll get the mister on the hose going and try to rub them off with water. Once they're mostly gone I'll spray with neem. Following up every couple of weeks with neem should keep them under control... (no idea what they are called...)

You have mealybug. Get some Nature’s Way from the green shed. That should fix it read label re application.
Cheers
Kirky

Excellent

Can i chuck it in a bucket of water for 24 hours and just drown the blighters? being a Mel the plant should be hunky dory

You could try .
24 hours may not be enough. Lots of bugs hold a small amount of air around their bodies and can survive for quite a long time underwater. I think some soap in the water would help wet the bugs and reduce the air bubbles.
Eggs may also not drown and will hatch out so, if the drowning works you will probably need to repeat before any new hatched reach maturity and start laying new eggs.

By soap? do you reckon i should spray the whole tree, under leaves, with soapy water first, leave for 5 min, then submerge, then to repeat after say 2 weeks or 1?

I think Neil is suggetion to put some soap in the water that you are going to soak the tree in. Just some dish washing liquid will do the trick. You can also use the same water n soap to spray them after soaking you willneed to reapply after any rain and as eggs hatch etc... Over a few weeks.
Cheers
Kirky

thanks Kirky. I'll take pics of the process

Yeah, wot Kirky said.
The soap should overcome the wax/oil/fluff that tends to repel water so it will be more inclined to stick to the hairs and bodies of the bugs, leaving less room for air pockets around them.

Let us know what happens with this experiment please so we'll all be better informed.