I'm not a fellow Britt but Holland isn't that far away !!
Try Thomas Cook, one way standby ticket to get from Punta Cana or La Romana to there and then a last-minute roundtrip to come back, sacrificing the return flight. For this check out
www.rainbow-flights.co.uk. Others have told me to get a PTA ticket, which is a roundtrip from here but prepaid in England. Never tried that but should also be cheaper.
Good Luck,
C.B.