Thanks for your reply.
On Harold's birth certificate, he was born at the address of Mrs. Pamplin's parents, and his 'mother' - who gives her name as Sarah Anne Nicholls (father blank), gives the address that Harold is at in 1911. So he is either fostered or illegitamate, or both.
After finding the photos this weekend, it is reassuring to know that Harold had on-going contact with the Pamplin's, and that my previous research hadn't been in vain!
I hadn't spotted May Ellen previously, so I will look her up.