The numbers on the tag. Should say HSS on one side and something like 1234/12, which is the sheep's individual number followed by the year it was born.
If it doesn't have this info then it's not actually a Heb registration tag.
You should also give Vicky the UK number on the EID tag, and if you have it, the sellers name, plus your details - name and address. I'm not sure if she would need your flock ID. There is a transfer fee of £1.