First time in 2.2 years that I’ve gotten a P0456. Just checked my gas cap, going to wait a couple days and if it comes back I will investigate the canister under the rear.

Anywhere else recommended to check while I’m poking about?

 

Yes... the charcoal canister vent valve.

By design, it is open almost all the time. The only time it is closed is when the non-continuous EVAP monitor runs, to check if there is an EVAP leak.
Remove it and apply 12 volts to it. Blow in the opening on the same side as the electrical connector. With 12 volts applied, it should be sealed tight and have ZERO air flow.

If you are able to blow through it at all (again, with 12 volts applied) , it is leaking and needs to be replaced.

If it has ZERO flow, then it is time to look at other parts of the EVAP system.
(My guess is the vent valve is leaking!)

 

IIRC I think it was the vent valve that was replaced when I bought the car. Will definitely have a look at it, checked out the access and it doesn’t look too bad.

 

Make sure to be gentle with the 10 mm bolts, they can break very easy. Try spraying them with WD-40 or your favourite penetrant a few hours before attempting to remove the cover.