When it comes to yew, it seems to me you have 2 choices:
1. Go the distance and cut your own. Turn it into a holiday and adventure. I did. My wife and I drove 4,000 kms this past summer out to the west coast and Vancouver Island, and brought home a truck load of yew. Both staves and boards. Enough to keep me busy for a long while.
2. Pay through the nose for it from the lucky people who live close enough to harvest it. Those will be few and far between. Also, what I consider bow quality wood may not be the same as what they consider bow quality wood.
I've done both, but I strongly recommend option 1, after becoming very broke and frustrated with option 2. Just sayin'.
It all depends how bad you want to make bows out of yew. It's a good option for the bowyers in yew country, but not so good for the rest of us. There are many other good options.