Use the Avios calculator to figure out how many miles you'll need on a segment-to-segment basis. BA miles are great for point-to-point travel, but it becomes insanely expensive if you want to add stopovers.
http://www.britishairways.com/travel...b#CalculatePod

I've found the best redemptions for BA miles to be YVR-HKG in CX First for 180,000 miles, LAX-NRT in JAL First 150,000 miles, or YVR-JFK in the new CX business for 50,000 miles return.