I am also researching my family history of 'Carrolls' all or mostly from the heart of the old East End. From what I've discovered so far there were lots and lots of them. My great grand parents (William & Joanna) had 14 kids! I haven't got all of their names yet but 1904 is in the frame - if Harry grew up in Hoxton/Shoreditch there might be a link. Drop me a line if any of this info sits with what you've got and we can go from there. Good luck!Steve Carroll.