I reckon 30 pouches ought to see me through a year very comfortably, so that's 1.5kg. I very much doubt I'd get into troub for that.
Essentially, it seems as long as the car isn't stacked to the gunnels with just me in it (going with at least two friends) we'll be fine and dandy. I know Mr Martypants isn't a smoker, but then I do believe his Mum may be, so it's possible we'll be using his 'allowance' for her.
Think it's more single passengers driving a Bedford that they're looking to catch!