Petop,
Did the same myself a number of years ago (not too many - 6th anniversary on Saturday this week!) but started the trip out of Bahrain rather than Afghanistan! Flew to London on took Delta (DL) out of Gatwick (LGW) in Business class via Atlanta (outbound) and Cincinnati (inbound). Great flights, good transfer, good timings, good price. Left London Fri a.m. arrived USA Fri p.m. Married Sat a.m. Honeymoon Sunday and returned Monday! Good flight back apart from all the golfers/commentators from the bloody Masters! Highly recommend DL.