SOE was a bit of a cowboy club like the OSS, some say. Also seems to have been full of marxists of various stripes, and aroused the violent resentment of other similar organizations IIRC, M16in particular. That would be one reason for purging their files: so the organization could not be easily reconstituted if needed again; or politicians merely decided it was. Probably it also contained many very talented and original individuals well able to "think outside the box", but when peace is declared the "establishment" generally tries to put things back where they were before "the recent unpleasantness" so rudely interrupted routine! LOL. Hence for example the disappearance of the Machine Gun Corps and the near disappearance of the Royal Tank Corps after WWI. In the later case the senior officers of the Corps cleverly got the King to become Colonel-in-Chief which scotched the plans for outright abolition.
Richard Meinertzhagen, not necessarily an entirely reliable witness one must admit, stated that before the war he was working on a plan with Lawrence and Churchill and perhaps a few others to somehow amalgamate Britishintelligence, and perhaps counter-intelligence services. He states in his memoirs IIRC that after Lawrence's death, he had to give up this plan. Now it so happens that some odd events surrounded Lawrence's death. Could there be a connection? Not likely we'll ever know.