Agree with Minesthechevy. At large UK airports details of actual stand sizes for aircraft types is normally published in airport's internal documents. As a general rule though when a stand is designed as MARS (Multi Aircraft Ramp System) it means the left and right side can be allocated medium size types up to 36m wingspan eg A320/B737 types. When the middle line is used it is normally at least B777/A340/B747 size but left and right sides cannot be used simultaneously. Just as the middle line can't be used when smaller types are on left and right.