you should have received a letter at the time telling you that they had taken over your employment, and your employment start date was the date when you first started with your previous employer.
If not then you will have to show the continuous employment.
Whatever your views of Remembrance, the point of the Poppy Appeal and the Poppy is to remember the sacrifices made by the sevices in all wars , it is remebering their sacrifices and to raise funds for the well being of ex-servicemen and women, who need support as Governments of whatever...