Welcome to FT
Never had a problem with UA consolidator fares. We usually book through USAirtours or Trailfinders. USAirtours is consistantly cheap and I've yet to have a problem with availability with them - highly recommended. We always get the miles.
UAL's free flights to the US used to be 40,000, they're now 50,000 but that's still abargain if you're earning 20,000 per return (300GBp jan-apr) flight. Spend 50,000 on a flight to Hawaii in Jul.Aug and you save a fortune (need to book in advance though)
Also you'll find *A useful for lounge access anywhere. CO will be a tad limiting and OW is a pain to earn miles/status on.