Hi, I was also born in the UK in the 80s, but I don't live there any more. Did you read any Enid Blyton growing up? I always liked George (Georgina) from the Famous Five books. Perhaps shortening it to Gina instead would work for you.
How did I choose my name? Er, my wife suggested it and I thought "yup, that'll do" :3 There aren't a huge number of names that work in both English and Japanese.