I remember we discussed about Sid Mc Ginnis with Ingo some years ago (or was it some decades ago....)
And we concluded that the most likely was :
Sid Mcginnis played some backing tracks, or maybe rehearsed with the band to try some ideas, BUT Mark played all guitars, or at least re-recorded his parts along Sid's backing tracks, and all guitars you can hear on MM are played by Mark
then,according to oldfield's book : after the record, Sid was asked to play on tour, but he was too expensive , so the band searched for other musicians, and then came Hal and Alan (their auditions are explained in detail in the book).