The way the text was written is ambiguous. It should have been written "A GCSE or equivalent qualification tested/examined/given in English" or something along those lines.
If you think the UK has language issues, come to the US where The Man® panders to every alphabet and language on the planet. People like me are oh soo insensitive for suggesting that English should be made the official language. I cringe when I see voter pamphlets in Spanish, Vietnamese and Russian. What's next? Hieroglyphs?