I would say the Cliff Webb item ought to be at the society of Genealogists. There are over 700 items listed in their library catalogue either written or transcribed by him et al.
But on FIBIS is this. (Which while relating to India, seems pertinent)
Previously there was a dataset called "British Overseas Marriages" 1818-2005, included some transcriptions of marriages at St John's Calcutta and, in spite of the dataset title, appear to be from the late 1700s/early 1800s. These were transcriptions, elsewhere [2] stated to be from records at the Society of Genealogists, and were very limited in information. Only the year of marriage was given, and there were no details of the spouse. See Calcutta for possible sources of these records. There were also records from other counties in this dataset. However, this no longer exists as a separate dataset, but appears to have been incorporated into the British Armed Forces and Overseas Marriages dataset above, as British Overseas Marriages (Cliff Webb Collection).
Perhaps an email to the Society would be useful?