Any question answered...

@ewanmac: do you have spoke key with you? to get you home just get roughly true side-to-side to stop it rubbing on the wheel, sort the finer details later.

imagine looking from the nipple end of the spokes towards the hub, turn clockwise to tighten, anti-clockwise to loosen. find the patch that rubs worst, loosen the spoke closest to that point, on the side it leans towards. tighten the closest spoke on the side it leans away from. don't go crazy, maybe do half turns to those, then quarter turns on the next ones further out. check repeat.

Awesome - thanks for that. In the end I completely released the front brake and rode home with a wobbly wheel. I think any attempt I may have made at truing may have made it worse :). On the way home I stopped by the lbs who straightened things out again but they said that the wheel was near-dead as they had already had to reshape it pretty vigorously after a crash. May be on the lookout for a new front wheel for the training bike soon.