The Whirlwind was effectively replaced by the Hawker Typhoon and Hawker Hurricane IV in 1943. The Whirlwind only equipped three squadrons, one very briefly (25 Sqn), and saw most service with 137 Sqn and with 263 Sqn, which our AH Typhoon also belongs to.
It had 4 x 20mm Hispano Mk.I Type 404 cannons in the nose and 60 rounds per gun. Eventually they made a Fighter-Bomber version which could be equipped with either 2 x 250lb bombs or 2 x 500lb.
The powerplant was 2 x Rolls Royce Peregrin V12 engines which were based on the RR Kestrel engine. These were rated at 885 hp at 15,000ft giving it a top speed of 360mph (or 270mph as a Fighter Bomber). Diving speed was around 400 mph.
As Karnak mentioned, there were only 114 (67 of which were converted to Fighter Bomber variant) aircraft produced out of an original order for 200.
Nice plane, lot of potential, but poor engine choice sealed its fate. Since all the RR Merlin engines were in demand for single engined fighters or heavy bombers, the Whirlwind really didn't stand a chance. It was completely obsolete by mid-1944.