What planes do BA use for London-Barbados, is the leg room good in cattle class and do they have seat back video screens ?

Currently, BA uses 777-200 for LGW-BGI.

It is not the airplane that determines the seat space, but the way the airlines has them configured at the factory. In our experience, b
A has the tightest configuration of any we have been in in coach. Thus, I would try to upgrade to coach plus, if they have that on that flight. Coming back from Europe, one can always get up and walk around a bit,but if it's an overnight, and you need to arrive there somewhat refreshed, it is hard to get any sleep in coach. Tried it a couple of times. UGH!

Please note that airlines may change aircraft or seat configuration, depending on season to optimise yield.
They should all have seat back videos. Contrary to the previous poster's view, I don't think BA pitch is any worse than other carriers in the coach class. Certainly they are more spacious than charter flights out of London. BA does have premier economy on this route--if you want to pay nearly double the fare.

777, no, yes.

legroom tends to be 31-32 inches on Ba international flights in ecconomy