Nice quiz! But note Gibraltar is a British Overseas Territory, which means that it is not a part of the United Kingdom. Therefore, Spain doesn't border the UK.
On your countries bordering Spain quiz, Gibraltar is there with United Kingdom in parentheses. Also, Wikipedia is not reliable because anyone can edit it.
That particular edit on a starred quiz was made by the quizmaster, not by me. On all of our non-starred quizzes you will see that Gibraltar (UK) does not appear in the Countries Closest lists.