Some great responses from many people here. Can't thank everyone, so I'll thank you all at once!
That's the part I find most amusing, people are assuming no more viable tenements, and no positive results for drilling in the area,
I feel they're quite wrong on that one. AA DYOR.
I don't expect Cattlin to sustain many, many years of heavy production of ore extraction, but with Lithium costs up, you can go deeper etc. and move more overburden / blast etc. so things previously unheard of become viable. I think a small drilling campaign, and buying good tenements in the area with pegmatite swarms, would work out fine. Failing that, you could even truck ore to the plant from a distance, that's also a no-brainer.
As someone else mentioned, if you really, really have to, you can break the plant down and move it, obviously not a preferred option due to downtime of production, but why waste a fully operating processing plant with many new components.. and you can move it to an outstanding ore body.