I'm not sure if this applies to your situation or will help ... but I too have an ancestor who appears as born Germany British Subject in some of his census entries. He was in fact born in Germany and came in England about 1850. I have checked at the National Archives and cannot find any nationalisation certificate for him. I did however come across a naturalisation certificate for his English wife, who was as far as I can tell from legislation obliged to re-apply for her English status on the death of the husband (even though she was born British, marrying a foreigner required the woman to in effect surrender her nationality to that of her husband). See this thread
http://www.rootschat.com/forum/index.php?topic=26899.0The sugar bakers/refiners of the East End of London was an industry predominantly owned and run by German emigrants who brought their skills to England (the labour tended to be split between those of German origin and local Englishmen).
On tracking down the birth record, there are some good sites (usually in German), Berlin Bob might be able to help you out on this bit .... Here is one I've used before
http://gedbas.genealogy.net/index.jsp also this might be worth a look
http://art-science.com/agfhs/index.htmlGood luck, it will be interesting once you have solved this, so please let us know.
Regards
Jonathan