im looking for the same from punta cana
but i heard all those english charter ticket like thomas cook or thomsonfly can be purchased from the aeroport on the day of departure!!
It is possible to book one-way flights from POP to LGW via Thomas Cook 809 320 0611 and Thomson 809 586 8165, subject to availability and, I believe, within 14 days of departure. Flight time is approx. 8 hrs. Their offices are located on the 3rd floor of the Scotia Bank building in Puerto Plata (opposite Tropical supermarket). Last price I obtained was $525.