Thanks for the input!
Mr flyingbee has now decided that the weather in Vancouver and Seattle isn't good enough when there are redemption seats available (err - that's why seats are available, because everybody else is thinking the same thing).
However, a big ^ to Mr flyingbee, because he has decided that we are going to go somewhere with our miles in CW later this year, where ever we can find availablity and some decent weather. So we might be spending a few more miles than originally planned, so I think the HHA will now be necessary. I think we may have to wait until I have had my April business trip miles posted to have enough miles to go further than North America. I'm liking the idea of taking advantage of a free stopover. I think we are going to have to be imaginative and flexible.
As an aside, and completely irrelevant, I have just arrived in the UK on a BA flight that is operating despite the strike. My parents just picked me up from the train station, and on the way home I was explaining that I was hungry and was there any nice cake at home. They asked if I had any food on the plane, and I explained that despite the flight leaving at lunchtime, it is only birdseed on offer, so I had made sandwiches at home to eat on the plane. Anyway, Daddy hadn't heard me use the term birdseed before and he thought it was very funny!

And the answer to the any nice cake at home question - Weight Watcher's cake slices...