Is UUA worth it? For me it is, and probably still will be when the rates change in April.

Mrs BF and I are flying LHR-JFK and back in May for under £1k each in CW having UUA'd from WT+. Those flights were retailing at £2.5k each in CW at the time of booking. That's a significant saving as far as I am concerned and makes UUA from WT+ to CW an excellent use of Avios.

Having said all that, I wouldn't consider a long haul flight in anything lower than WT+ and haven't done so in 15 years. So although a trans-Atlantic fare of less than £500 might seem like a bargain for some, it's irrelevant to me.