In general, one can expect the average magazine (Q, NME, Melody Maker, Sounds, Vox) to report the regular John Martyn release. The Big Muff Bibliography deliberately leaves out the various reviews that have been published. Main reason for this is the average review being rather short, and often badly written by an ignorant editor. However, if some future historian were to become interested in the critical reception of John's work, he or she might find the following info useful. You can also look into this table when you want to judge a vintage magazine offer.
Additions are welcome in my mailbox of course.