I have some very fine Past & Present comp cds. They seem very well researched with info on the bands/ singles contained within - particularly the "Picadilly Sunshine" series. Whether they have gotten hold of the original artists and copyright holders is another matter which reading the info on the Amorphous Androgynous "Psychedelic Bubbles Exploding In Your Mind" series can be very labour intensive indeed.
Do not expect recordings from original master tapes though ... mostly vinyl rips.