Don't know if it still happens, but when I was a despatcher a couple of decades ago there used to be an estimate based on the departure time from home base (for UK based aircraft), which was updated when they arrived at the far end, then again once they got airborne on the return leg, and finally when the crew gave the handling agent a call usually about 20 minutes out when they would have a good idea of the real eta. For Manchester I suspect that is still the case, as the eta often changes about 20 minutes before arrival (though not normally by too much). Not a problem for me as I only live 15 minutes away, but can see it would be a nuisance for those from farther afield.