Just tried my newley rebuilt front wheel in my forks, & of coarse, it is 2mm off centre. Too far towards the disc (right side).
Is it easy to pull it over? Do I just tighten towards the direction I want to go?

You should always work in pairs of spokes: in your case loosen a spoke from the disc side and tighten the opposite spoke on the non-disc side. You should work slowly, turning the spoke nipple only about 1/8 of a turn for each adjustment. Continue the adjustment process in pairs all the way around the rim until it's centered.

Flo — I have been building wheels for more than 20 years, and I have always found that wheels with offset hubs like those on Commandos and Triumph triples are devils to get right! I have found that in order to end up with the correct offset, I have to increase the offset by about 3-4 mm before the final tensioning of the spokes (but after the wheel has been trued). Otherwise, as you carefully and methodically try to tighten all the spokes to the same tension, your carefully measured offset will decrease and you could end up with the spokes on one side too tight and on the other side not tight enough. This is because the set of spokes on the 'dished' side has a significantly greater leverage than the opposing set and the hub is trying to self-centre in relation to the wheel rim. You may have to experiment with the 'over-correction' of the offset. Sorry if this sounds over-complicated and clunky but try it and see how you get on. I am not claiming that this is the only way of doing it, and others may have evolved their own methods, but it works for me.

Dave

Note to my previous post — maybe try 2 mm over-correction before you do the final tensioning and see how it works.

I gave it a go & got it within about 0.5mm off centre with the wheel running within a milimeter all round.
Presume this is good enough. There is a kink in the rim where it has been joined in production., can't do anything about this.
I can get a tyre on it tomorrow.
If it wasn't for the snow, I would had to have gone to the pub, that would not have been as much fun of coarse.

0.5 mm is pretty good as far as offset is concerned. The main thing is that the rim should be centred in the front fork. You should be able to reduce your runout by at least half without disturbing the offset or out of roundness.