Thank you Aelfric,
I've checked back through my papers and it is listed as a "matrimonial case, divorce, adultery" on the Lambeth Palace Library records where all these ecclesiastical marital disputes are located. I'm not certain of the procedure - whether all divorces needed a private Act of Parliament, but then the Court of Arches handled what were basically formal separations (yet it is catalogued as divorce etc) - no doubt it was a procedure far less expensive for the parties. For this couple I've seen no Act of Parliament for a divorce, so I suspect you're right, that it was a formal separation. The wife I notice didn't remarry until the husband was dead - which might seem to confirm that. This seems to answer the circumstances I'm seeing: the couple were rather "separated" in legal terms (but not in the eyes of God) and were in a kind of marital limbo. Not free to remarry and, certainly the wife, would have been restricted in what she might do without the husband's consent (i.e. business dealings). The would perhaps explain why she could not testify against her estranged husband. I've come across this separation arrangement before where it was particularly hard on the wife as (in the 1680s) she was entirely dependent on the hostile husband for support. Thank you for helping me inch towards some clarity!