Unless things have changed, you'll need to re-check your bags. It's a hassle, but not the end of the world and although it says you'll be leaving from a different terminal, it's all in the same building. These threads might provide some useful info, and I believe there is a Meet and Greet service offered by BidAir which may or may not make things smoother for you.

https://www.flyertalk.com/forum/brit...fer-jnb-2.html
https://www.flyertalk.com/forum/brit...ction-jnb.html