yew advice please

I work in a garden where there are lots of self sown yew. I have no experience of these trees. Some of them are 15cm thick and all are dead straight with no taper. Is it worth while collecting these trees for carving or am I just wasting my time ?. If they are worth digging what is the appropriate season (we are in the first month of winter here), and how much root is required for them to survive?. I live in one of the coolest parts of the country, yew are rarely seen growing in most parts of Australia.
With thanks from Craig

Lucky you!

If it is possible and there are many, I'd have a very good look at each of them and chop them at various (low) heights, and leave them to develop in the ground for a few more years. The ones with the very best potential could be lifted next spring for more rapid development.

Hi Kev there are about a dozen that I have found so far, the property is about 10 acres so I haven't had time to explore all of it. I have cut some of the trees down to about 1m and shortened all the branches back to around 6 inches, do you think I should reduce them more ? How much growth should I leave for carving ?
With thanks from Craig
ps this place is also a blueberry farm( yum ) and there are two rows about to come out so will have to get in amongst them as well