I make my own quite often (not quite a big as those bad boys . You do tend to discover that mince is pretty tasteless unless you chuck quite a lot of stuff in it.
You could try any of the following in addition to salt and pepper: cumin powder, fresh thyme, rosemary (chopped very small), tarragon, mustard, (Worcester sauce or Oxo, like you were thinking), parsley, veggie stock powder, chopped fresh chillies, ketchup - the list is pretty endless. I avoid raw onion, as that's all you end up tasting.
Delia Smith moment now over..........