I too, am slightly surprised at BA's decision to take this route up; I sincerely hope this is not another "boom & bust" destination, as the others now being axed, were; one also wonders whether the route is viable, given it is only being flown once a week.
Considering BA have vowed to chase premium customers & their credit cards, it would seem that the difference between flying to these destinations, and axing them later, is a pretty close-cut affair-any reduction in the number of premium travellers on these flights (whether seasonal or otherwise) will quickly hurt BA where it matters; perhaps PLS will turn out to be another Barbados, in terms of pax yields.
The flights are indeed from LGW; the flight number outbound is BA2253, departing at 1010, arriving PLS at 1730.
Rtn is BA2252, departing PLS at 1910, arriving at Gatwick at 1110, the morning after.
BA had realised what a huge mistake it was to charter a/c with such tightly-packed configurations-they were not commensurate with the standard BA product-and were an embarrassment to operate, in that sense; they are now slowly being withdrawn (or reconfigured).
Let's see how long it takes before they change their mind again!