Front brakes went choppy, that is as I apply force to the handle it starts breaking slightly and then suddenly the braking force jumps quite a bit and the bike lurches. Is it a sticking piston or a worn master cylinder or something else?
Disks are in decent condition and and pads are a 1000km old.

I'd say its warped discs personally.

fork bushes,
lose brake mounting nuts,
lose headstock bearings,
lose brake disc mount bolts,
fucked disk bobbins,
warped/cracked disc,
fucked braked pads,
worn seals in the master cylinder,

as you can see theres quite a few posibles but check the simple things first like nuts and bolts are torqued correctly

How to check for warped discs?

Stick your bike on a stand, abba or front paddock (just get the front wheel off the ground) and rotate your front wheel without applying any brake pressure at all.

If it spins freely without catching at any point then gently, and I mean gently apply a tiny amount of brake pressure and see if the wheel catches stronger at any point in its rotation.

If the wheel catches badly, like mine does at the moment (looking for new discs which won't cost me my leg), then you've got one or two warped discs.

But while you've got the bike up supported I'd also check for freeplay in the entire front end, and as porndog says, check everythings torqued up correctly.

You will know if it's warped disks because it will feel like the brakes are pulsating when you're on them. If it just lurches once and then it's constant braking pressure then I would say worn seals or bolts not torqued correctly.