Trade between England and Iceland was common from the end of the 14th century, which is longest distance of open sea I can think of. Although it's unlikely they would sailed from England directly, but gone up the coast of Scotland. Iceland was known of in England prior to the 14th century, but there are no records of visiting ships from England before then.

(https://books.google.co.uk/books?id=paq91FA5fu8C&dq=english+trade+with+iceland+medieval&source=gbs_navlinks_s)

As I understand it, most medieval ships hugged the coasts as much as possible, I don't know whether that counts as having 'made land' or not.