Whilst the title of 'Common Law Wife' has no legal understanding, it is actually a valuable 'statement' to show that a serious relationship is involved and this is not some 'one night' stand. In these so called enlightened times it can be very helpful in showing the true nature of the relationship, particularly if a child is involved.
An SAS soldier killed in Africa (Bradley Tinnion) left a 'girlfriend' and a child and a RM Major killed in the gulf had a child and his (Swedish?) female friend was able to prove paternity and his child was accepted as such - not sure about the lady.
Whilst too complex for me to fathom, I suggest as I did at the beginning of the topic, to engage the various experts - including the Forces Pension Society.
Old Duffer