Yes, first mistake goes to me. I have been calling "Charles Pemberton" by the name "George Pemberton".
To explain this error, the reason Hijikata would think of him as "George Pemberton" is because he was going by that name during the time he lived in India. His full name is now Charles George Pemberton, so it was his middle name. However in England there is another "George" - Dr. George C(hristopher) Holcroft. In order to avoid confusion, Pemberton began to go by his first name in London. Of course, since Hijikata knew him before, he still sometimes thinks of him as "George Pemberton".