Taking car seat as hand luggage on ba flight? [Title edited by MNHQ at OP's request]

[FluentOpalMaker]

Anyone can help on travelling with car seat on BA flight. We have DS - 5 months and I’m trying to find out if we can take our car seat (maxi cost pebble 360 pro) and store it in cabin as hang luggage. We taking car seat because we will be driving during our holiday and I don’t really want to check in the car seat.

https://www.maxi-cosi.co.uk/c/flying-your-child-can-i-take-my-car-seat-plane

the seats on planes are very narrow. So there are only some seats you can use.