It's not definitive by any means, but I rather enjoy the lesser-known Muir Mathieson version with the Sinfonia of London:
This is my favorite also. It has less of the period source music and more score. Also the last half minute was used for the WOR 9 "Million Dollar Movie" theme in New York in the 70's and 80's. It's beautiful.
"Million Dollar Movie" originated with WOR-TV in 1954. They had films from the RKO library, which they would repeat every night for a week. KING KONG and THE LAST DAYS OF POMPEII were highlights for youngsters. I believe the logo was a movie slate shown against the city's nocturnal skyline. The music became familiar to us long before we encountered GWTW in the 1961 or 1967 reissues.