So I found a flight on skyscanner for British Airways that I've been eyeing for quite a while. However, it is a basic economy ticket which means that it doesn't come with a checked bag and seat selection included in the price. I was wondering if I could purchase the ticket off of the third party site, put in the code and selection into British Airways' site, and add on a bag and seat selection onto it for my trip for an extra fee? I wanted to do this since I've been searching for the ticket for awhile on British Airways' site but they seem to not have it, or it's very expensive.
I figure that adding on the baggage fees and seat selection will equate to just me paying the same price as a main cabin ticket, which comes with one free checked bag and seat selection.
Thanks in advance!