Messerschmitt Bf.110C - Foreign Users

The Messerschmitt Bf.110C was used by many foreign users:

• United Kingdom: At least one Bf.110C-5 was captured by the Royal Air Force and was assigned to the famous No.1426 (Enemy Aircraft) Flight of the Royal Air Force, which evaluated captured enemy aircraft. They were based at Collyweston, in Northamptonshire and by 1944 it was still in service with such unit. 
• Italy: When the Regia Aeronautica formed night fighter units in 1942, they realized that they lacked competent night fighters, so they bought various second-hand Bf.110C from the Luftwaffe. They were assigned to the 1º Centro Sperimentale (1st Experimental Unit) at Guidonia test centre in Lazio in order to train pilots in night flying conditions during summer 1942. When the training was over, they were assigned to the 60º Gruppo (60th Squadron) in the 41st Stormo (41st Wing). They operated from Lonate Pozzolo, in Lombardy. In September 1943, when Italy signed the armistice, the units were disbanded and the Bf.110C were taken back by the Luftwaffe.
• Romania: The Royal Romanian Air Force received some Bf.110C when they formed the Escadrila 51 Vánátoare de noapte (51st Night Fighter Squadron) which was trained in night flying conditions using outdated Heinkel He.112 fighters during 1943. The Squadron was integrated into the Luftwaffe NJG.6 as the 12./NJG.6 and took part in the aerial defence of Romania during 1943 when the USAAF launched the Operation Tidal Wave, the bombing of Romania's petroleum fields. They were active until 1944 when Romania switched sides and the squadron was disbanded and the remaining aircrafts (the squadron had sustained heavy casualties) were taken back by the Luftwaffe.
• USSR: Apparently the Soviet Air Forces bought at least one Bf.110C-4 for evaluation purposes in Autumn 1940. It most probably served as inspiration for the Petylakov Pe-3 and the fate of the Soviet Bf.110C is unknown.
• Kingdom of Yugoslavia: When the Axis invaded Yugoslavia in April 1941, the Royal Yugoslavian Air Force managed to capture at least one Bf.110C which was quickly repainted in Yugoslav colours and used most probably for propaganda reasons. After the fall of Yugoslavia it's fate is unknown, but it was most probably either taken back by the Luftwaffe or destroyed.

Sources:

1. https://en.wikipedia.org/wiki/Messerschmitt_Bf_110#Operational_service

2. https://www.rumaniamilitary.ro/aviatia-militara-in-al-doilea-razboi-mondial-suedia-vs-romania-partea-a-iii-a (translated)

3. Salamander Books - The Complete Book of Fighters