Welcome to Flyertalk Brink007, it's good to see you here in the BA forum. We like to welcome new members and I very much hope that you will continue to participate here. Welcome on board.
I think you've had the answer on the Upgrade using Avios option, there are some dates available by YVR and SEA aren't great for Business Class availability at the moment. SEA is unlikely to change, but YVR may do so over time.
You can reduce the cost of the Club World ticket if you start from different places such as DUB (£2112), AMS (£1975), OSL (£2080), LIN (£1863), WAW (£2110), LCA (£1933).