Night Owl - G-INFO is just one such public source of such information, but it doesn't tell you anything about foreign reg helicopters operating from UK bases, which G- reg helicopters are operating or stored outside UK, accident data, etc etc.
ler1992 - what's your angle on finding this information, career prospects or what? If we can understand the Q better, we may be able to help better. Is it just offshore fleets that interest you - as your Q suggests?