It rather depends on what you are going to do with this aircraft.
If you are flying it, how do you know its provenance and maintenance history and that of its engine and hence how did you get a CofA or whatever? When you acquired it, did you not also get the wad of documentation built up over its life?
From my own rather cowardly point of view, I'd be more concerned that I have an audit trail of this aircraft's operating history than worry too much about who used it in any detail.
At DORIS in the RAF Museum Hendon, they have a microfilmed copy of the Aircraft Movements Card and this will tell you to whom it was allocated and when.
Old Duffer