From the New Yorker (full text not available):
Visitors to Britain are rarely able to grasp – sometimes after decades of residency – the vital distinction its inhabitants make between complaining and moaning. The two activities seem similar, but there is a profound philosophical and practical difference. To complain about something is to express dissatisfaction to someone whom you hold responsible for an unsatisfactory state of affairs; to moan is to express the same thing to someone other than the person responsible. The British are powerfully embarrassed by complaining, and experience an almost physical recoil from people who do it in public. They do love to moan though.