I've just noticed my front wheel is not centred within my front fork and is off to the left, which is causing the right v-brake caliper to lean over towards the left also. How can I fix this? I've tried taking it off and rebolting it back in, but it just goes back to the same position. Thanks for any help!
I've just realised, that I recently overhauled the bearings and perhaps have reinstalled the axle at an incorrect length, causing the wheel to push over to that side? hmm I'm not sure
Try putting the wheel in the fork one way, then flip it and put it in the other way. If it is too close to the OTHER side after you flip it, that tells you the wheel itself is not centered. If it's always to close to the same side of the fork regardless, something is up with the fork or dropouts.
It should be pretty easy to see if you put the axle back in wrong.
DaveM is correct, but you may need more explanation. If the wheel shifts from one side to the other when you flip it then the rim is not centered on the hub. This can happen if someone incorrectly trues the wheel (Google "wheel dishing" - sheldonbrown and parktool sites are best) or if you overhaul the hub and leave out a spacer on one side. Not possible to reinstall the axle "at an incorrect length," at least not in such a way that it affects centering. Given your apparent level of experience it may be best to hire or get in-person help (bike co-op nearby?) with any wheel truing.
If the wheel is still off center in the same direction when you flip it then either the dropouts are misaligned or the fork itself is bent. Special tools are required to fix either problem.