I may teaching granny to suck eggs here but.... When the flowers have finished or are looking tired on the daffs, deadhead them, but leave the stems until they're completely brown. This means all the nutrients have gone back to the bulb. You can then lift the bulbs & let them dry. You can then save them until September & plant them in pots / beds / lawns. If they're already in the lawn, try not to mow them until the stems are brown. Good luck.