Heavy tank
The Char 2C was one of the largest tanks ever produced. At the start of World War II, France and the Soviet Union were the only countries to have inventories of heavy tanks, such as the Char B1, T-35, and KV-1. The Matilda II was designed under the British infantry tank concept which is similar to the heavy tank having thick armor and weighing more than their other tanks. It’s usually separate because they have less firepower with their cruiser tanks (comparable to mediums) at the time having the same main armament but more machine guns. Later war examples were the German Tiger I and II, as well as the Soviet IS series. Note that "heavy" versus "medium" is more a question of tactical roles than weight; the Panther, for example, was a "medium" tank that outweighed most Allied "heavy" tanks.
Tank destroyer
The closest the British came to developing an armored tank destroyer in the vein of the German Jagdpanzers or Soviet ISU series was the Churchill 3-inch Gun Carrier—a Churchill tank chassis with a boxy superstructure in place of the turret and mounting a 3-inch anti-aircraft gun. Although a number were ordered and fifty delivered in 1942, they were not put into service as the immediate threat passed. The design was rejected in favor of developing a 17 pounder armed Cromwell tank variant, ultimately leading to the Comet tank. The Tortoise "heavy assault tank", intended for use in breaking through fixed defensive lines, was well armoured and had a very powerful 32-pounder (94 mm) gun, but did not reach service use.