CO's BusinessFirst is a solid product and IMO more than acceptable even if you end up in the old seats. It's not as if UK-NYC is a 12 hour flight. I've only tried AC once and didn't find it to be anything special -- certainly not special enough to be worth adding connections.

LX is reputedly in a different class, to pick up on lallyr's suggestion, and might be fun to try. But you'd be paying a hefty time and convenience premium.