@mobius, I’ve settled on ordering 3-4 (250g) bags about a week before I think I’ll run out. Since the Christmas madness allowing a week for shipping seems to have been enough. I’m then using everything in the 1-5 week range, and I’ve been pleased with the taste and it avoids too much faff.
The only issue is a few too many unplanned coffee drinkers. If that happens Sainsbury’s usually have a not too old bag of Union on the shelf.