i’m from the cup and cone generation need to replace rear sealed bearings on a cotic branded hub so I’ve removed the cones both sides and the freewheel, can see the bearings clearly – have given each end of axle a few knocks with hammer and a block of wood – do i just hit it real hard?

Not necessarily, depends on the hub, but some have an axle that will only come out from one side of the hub. Chances are that it does just need a heftier hit, but i’d check with the manufacturer first.

but some have an axle that will only come out from one side

that’s what i was wondering but can’t see anything that would stop either bearing like a lip but doesn’t take much – cotic came back to me very promptly with the bearing size guess I’ll drop them another email – was hoping to get done today 🙁

It won’t be visible from outside, some have a stepped axle in the hub shell that won’t pass through the freehub mounting bolt, so needs to be removed hub side first. Also worth checking your brake disc doesn’t overhang the bearing if it’s still fitted.