The introduction to each Scott catalog lists all of the omnibus issues. It also lists all the countries/colonies (with catalog numbers) that issued stamps in the set. It doesn't give an omnibus set total, but you can count them if you desire.
Set total 106 stamps: Mint $169.10 Used $117.20 which includes stamps of different designs that are included in the omnibus set. (Source 2019 Scott Catalogue)
I hadn't looked at the Gibbons listing of British omnibus issues before. They have a different take on listing them. I do like the cross reference table where they list all the omnibus issues and countries and show how many stamps were issued by each country,m including those countries that did not issue stamps for a particular omnibus set.
Scott's listing does separate the omnibus and "similar" issues related to the omnibus topic.
