Excellent - thank you both so much, I really appreciate your help.
In November 1943 when he was flown to the UK, he was interviewed by the Royal Patriotic School - this was more of an interrogation to determine if he was to be trusted or not. The interview states:
14. At the beginning of May, a call was made for members of the parachtist corps who might have something to fear if they fell into the hands of the Germans during the war. JONES put his name in on account of his past record, and on the 20th May about 27 placed similarly with himself were sent to Algiers to the recruiting bureau of the French area where they were provided with an opportunity of adopting another name. JONES said that he chose Pierre DARMONT, the real name of the French film actor Pierre BLANCHARD. He was told to wait until further instruction but the change of name was not put through before he left, and he did not hand in the extract from his Livret Militaire which he carried with him. "
I'd really like to confirm this and if possible to confirm the name he chose, as it may be the his code name for his MI6 operations. I think the diary mentions this change of name on Friday 24th May. I can just about get the gist of being 22 years old and a name - but it looks like Jacques.