As lovinglife suggests, I would ring NHS direct and ask for their advice.
In general though, even with a bout of food poisoning, I would continue taking my lantus (as this deals with the background energy that your body needs to keep you alive) and just stop taking my fast acting insulin if I were unable to eat.
If I was unable to eat for more than a day, I would reduce my lantus slightly for day 2.
But that's just how I would do it, best to give NHS a ring.