I am a little confused to say the least. Do you have a
positive date of birth or Discharge A number for your John Axon?
The only Record I can find in the series BT390 is this one. He would be a little young to marry Glady's
http://discovery.nationalarchives.gov.uk/results/r?_st=adv&_ep=axon&_cr1=bt390&_dss=range&_ro=anyBT390 covers Merchant seamen who served under T124X agreements. WW2 Merchant seamen who served on Merchant Ships requisitioned or commandeered by the Royal Navy. They kept their Merchant Navy pay and conditions but were subject to Royal Navy orders and discipline. (see also BT382 below)
BT391 Are similar to the records in BT372 and Covers Merchant seamen who took part in combined operations in Europe, during and after D-Day.
BT372 Covers Merchant Seamen's "Pouches" 1941-1972. Pouches can contain MN ID Card complete with photo details of qualifications gained and other euphoria. Also if a person had MN service before 1941 his/her records should be included in the "Pouch" Many of these records have been lost or destroyed.
BT382 Covers Merchant Seamen 1941-1972 and is divided into 7 sub series. Basically this series contains CRS10 forms, catalogued alphabetically in blocks of 60 names. They give the persons name, rank and details of vessels served on with the dates and places of engagement and discharge. This series also contains (In part 7) some records of seamen who served under T124 agreements. If it applied to your man it should be here
http://discovery.nationalarchives.gov.uk/details/r/C11001344For a detailed explanation see TNA's Research Guides.
http://www.nationalarchives.gov.uk/help-with-your-research/research-guides/merchant-seaman-serving-after-1917/I repeat. Unless you have a positive date and place of birth or a positive Discharge A number you will be forever running round in circles.