Welcome to Flyertalk
HolidayPrincess,and welcome to the BA forum, it's great to see new participants here, and so thank you for your question. I hope you also have a good trip to Barbados.
I am not well placed to give direct advice, but there are two links that may help you make a decision. In this forum's Dashboard there is a seating guide to the 777 series. Now that has a lot of versions now, and there are now 3 versions in LGW alone, so it does get rather finicky. The other place to look is thebasource.com and this appears to be your seat map:
British Airways B777-200ER 14F/48J/40W/124Y LGW Seat Map