Yeah its interesting and quoted throughout his biography by his once close friend Paolo Hewitt how plagiarism is a fundamental part of his song writing, he doesn't deny or attempt to hide it, in fact the opposite is true.
Probably the most famous :-
The Beatles Taxman
The Jam - Start
Taking other work and using parts of it to create something new doesn't detract from the finished artical for me, in fact I find it quite interesting, so much of his songs have little bits of old Nothern Soul records in there that many would not notice