From the wiki:
In 1947 the management of the plant in Pomigliano d'Arco passed from Alfa Romeo to Metalmeccanica Meridionale,[25] but in 1948 Alfa Romeo returned to aircraft engine production.[6] In 1949 Alfa Romeo made an alliance with Fiat, SAI Ambrosini and Aermacchi to produce de Havilland aircraft, with Fiat sharing responsibility for the engine with Alfa Romeo and the latter two companies taking responsibility for the rest of the aircraft.
and:
The revived Alfa Romeo Avio began to diversify its operation. Its repair and maintenance side expanded to deal with repairing Curtiss-Wright R-1820 and R-3350 piston engines, Rolls-Royce Avon and Wright J65 turbojets, Rolls-Royce Dart turboprops and Rolls-Royce Conway turbofans mounted on Italian and Norwegian airplanes.[2] Alfa Romeo license built the Bristol Siddeley Orpheus for the Fiat G.91 programme, one of a number of examples of cooperation between the companies during the decade, and was the European distributor of the General Electric J85 and CJ610 turbojets. It was also involved, alongside FIAT, FN of Belgium and BMW, in the European production programme for the production of a FIAT (General Electric) J79-GE-11A turbojet to power the Lockheed F-104 Starfighter that was being built in Europe and was used extensively by many NATO air forces.
no mention of de Havilland engines.
Just a passing mention of FIAT making the Ghost in the early 50's in an article of the FIAT Turbina.
FIAT G.80 was Goblin powered https://en.wikipedia.org/wiki/Fiat_G.80
Vampires were built by FIAT as well.