Is there a BOAC livery?
Unfortunately, I don’t believe there is but there are some cool feature requests you should check out:
Livery’s are designed and built by the IF team. The #features category is for suggestions. Take a look at the topics linked above by @Drummer. There you can vote for them and hopefully they get added in the future! I agree though, the BOAC is a beautiful livery.
Lastly, if you ever want to see if a livery is available in Infinite Flight, check IFATC.org and look under the “Airplanes” tab to see aircraft and their available liveries.