The aircraft was a 767-300, G-BNWH - the aircraft which almost always operates the MAN
Only info I found is this:
The Associated Press
January 16, 2004, 1:28 AM
A British Airways flight on its way from New York City to Manchester returned to Kennedy Airport after experiencing hydraulics problems, authorities said.
British Airways Flight 1502 landed safely shortly before 11 p.m. Thursday, according to Tiffany Townsend, a spokeswoman for the Port Authority of New York and New Jersey, which manages the region's airports.
Townsend said about 129 passengers were aboard the plane. No one was injured, she said.
Messages left for British Airways were not immediately returned.
I'm sure some more info will surface pretty soon - strange that it returned to JFK
so long into the flight - maybe they wanted to minimise passenger disruption.