The best option would have been LAS direct to Manchester in angled lie flat C class using BMI but unfortunately they are terminating the route very soon if they have not already done so. Thus, new best option in my view would be NZ C class LAX-LHR if it was possible. Generally I would avoid redemptions on UA F or C unless you were absolutely certain of getting their new product which is still doubtful. However, you might even prefer UAs abysmal normal F or C product to taking very indirect routes. Best option to get new UA C class would probably be domestic LAS-IAD followed by IAD-LHR on a 767.

Somebody mentioned LX, is their new C Class operation on some routes already?