I think there's issues with it being an organised charity. They will accept it if there's a guarantee that the food is acceptable. I can't give them that. There's even issues donating it to farmers for cattle apparently (although I think the farmer I spoke to thought it was waste bread rather than packaged untouched from a supermarket.)Best Before - why would that be no good for a food bank.
Use Before, or Sell Before, sure. Best Before just means it might be past its best, not at all that its no good.