Birth cert from refugee camp Coimbatore India 1943

[Bookbox]

would a researcher be able to access the real/actual document at the Brit Library?

Anything held by the British Library will be a transcript, not the real/actual document. Just email the Asia Pacific and Africa Collections team (APAC) at the BL, give them all the details of what you're looking for, and ask for advice. They will reply within 5 working days and are very helpful.

https://bl.libanswers.com/form

ADDED
You need to remove his name from your reply #3 above - this contravenes RC policy because he is still living.

[Jebber]

Generally a child takes his father’s nationality. Have you investigated the possibility that he was registered at birth as Turkish? You say his father didn’t become naturalised British until 1969 when the person concerned was already an adult of 26. It’s a complicated subject and regulations and  conditions vary and have changed over time.

[Kiwi Carol]

Don't know how to edit the offending info; was only trying to be helpful. There's no edit function...
Carol

[Bookbox]

There's no edit function...

There is - it's available for 24 hours from posting.

[Jebber]

Don't know how to edit the offending info; was only trying to be helpful. There's no edit function...
Carol

It’s on the right hand side of your post, next to ‘QUOTE’ only it’s called ‘MODIFY’ not edit.

[Kiwi Carol]

Strange... there is no modify next to Quote...