For the most part, the OSS and SOE agents simply packed up and went home again. The resistance networks they had established were no longer needed now that their host countries had been liberated. Similarly to the regular armed forces, now that the war had ended there was no need for such a large intelligence service, and so many cuts were due to be made. Both the SOE and OSS were disbanded, with some parts merged into other intelligence agencies.

For the former agents, readjustment to civilian live would prove difficult. Intelligence work was one of the most dangerous jobs in the war; of the 172 British agents sent to France by the SOE, 108 were killed.

Many more were captured and sent to concentration camps, and after their release found it difficult to readjust to freedom. In the words of Captain Steven Best, an MI6 agent who was kidnapped in the Netherlands in 1940 and spent much of the rest of the war in Sachsenhausen Concentration Camp:

Over France there was a brilliant white cloud beneath us which dropped in a sheer precipice as we came to the Channel; then, before us I saw a dense threatening black wall, cloud of England, which seemed to express my own fear that I was returning home to an England I did not know, myself probably changed beyond recognition and, as so often before, I wondered whether one has ever the right to go back ... I fought the battle which faces every prisoner who returns.

When Brian Stonehouse, who had been captured and sent to a concentration camp, returned to the United Kingdom he was invited round for lunch by some friends. However, when the pork chops they had bought were put in the oven, he was unable to remain in the flat, as the smell of burning flesh reminded him too much of his captivity.

Other agents suffered similar mental health problems. Many had nervous breakdowns, or ended up getting divorced. One agent clearly had trouble readjusting to law-abiding life and was caught trying to smuggle a plane full of gold and platinum to France. Most of the agents were released to civilian life, and re-integrated fairly well, however.

While SOE was closed down in 1946, 280 of its personnel joined SIS (MI6) where their experience of undercover operations and encouraging resistance proved invaluable during the cold war. One agent, Colonel David Smiley, had been sent to Albania during the war to encourage partisans and act as a liason. In the late 1940's he was sent to Malta to train pro-western Albanians and send them to undermine the Communist government.

For the members of the French resistance, the story was altogether different. France had been devastated by war far more than Britain, and resistance members could not simply go back to the lives they had lead before. Particularly in Western France, where the Allied advance had very quickly swept through the region, there was almost no functioning Government.

The French resistance had made a major contribution to the war effort. Their efforts on D-Day had majorly contributed to tying up German forces and disrupting their supply lines. Up to 30,000 had been killed in action, and a further 24,000 had been executed by the Germans. There was understandably some animosity between them and the French who had escaped the country and now returned expecting to carry on as if nothing had happened.

In Toulouse, a Maquis force had liberated the city, and the senior SOE Agent, George Starr, had an angry confrontation with Charles de Gaulle who had turned up to organise a civilian administration. The argument ended with de Gaulle calling Starr and his men 'mercenaries', to which Starr responded that many of them held commissions in the French army.

De Gaulle had a similar argument in Bordeaux, where he refused to allow Roger Landes, an SOE Agent, to sit in on meetings. He only relented when 4000 demonstrators demanded that he do so.

I've not really been able to find much on what happened to Russian partisans after the war, and it's entirely possible that not much has been written. I hope this has still been useful, let me know if you have any more questions.

Sources:

MRD Foot, The SOE in France, 2000

Peter Jacobs, Setting France Ablaze, the SOE in France during WWII, 2015

Stanley Hoffmann, 'The Effects of World War II on French Society and Politics' French Historical Studies, Vol. 2, No. 1 (Spring, 1961), pp. 28-63