How long do ghost carp live in a pond in UK about 8 meters by 8 and a meter and a half deep many thanks?

Ghost carp (Cyprinus carpio) are a cross between the Japanese Koi and the common Mirror carp. They will live for many years (20+) and can grow to immense sizes (1metre+) given choice conditions. In a pond the size you mention they could well live out a long life provided you don't overstock.