Carbon emission report calculation

Hi everyone, I’m volunteering for this science organisation and they were hosting a big event recently. I’m responsible for sustainability project and to calculate carbon emission and make a report. I really don’t know where to start I have all the data about attendees, from where they travelled, what mode of travel they used, same for speakers, all the venue details and waste. It’s just quite difficult to find straight forward guidelines for carbon accounting in the uk. I don’t have any budget either so calculations and reporting is all on me. How would you calculate carbon emission for travelling and hotel stays. I do have a postcode info so I was thinking about creating a table with distances between the venue and where people travelled from (three different tables one go train, then plane and car) then using function that matches the table with the mode of transport and origin city then fills out the travel distance. And then maybe applying different function that multiplies that again depending on mode of transport by the carbon emission factor. Any advice how should I do it? Thanks for your time 🥺🫶🏻