^ ^ to the Air Canada service through YVR. It's the fastest way to London, and the connection is very easy. I like their inflight product, especially for a solo traveller. These seats can be hard to get though -- AC is stingy with its business class award availability. They tend to make seats available closer to the time. I second taff_2003's suggestion: book whatever you can now, and keep your eye out for better options. It's only £20 to change.

The LHR-PDX codeshare isn't really nonstop. It's a United flight LHR-ORD-PDX. Not recommended.