I said yes to an update and my iphone6 was shut off and I'm not able to turn it back on

Did you already try hold the sleep and home button for at least 10sec, until the Apple logo comes back again?

After that connect to your computer and restore it again.

If you can't update or restore your iOS device

I've had the same problem, I have followed all the apple suggestions re turning everything off & on, trying a different PC, different cable etc etc.......do I now have to haul myself down to an apple store????

An Authorized Apple Service Provider can also check the phone, or you can contact Apple Support about that.

Find an Apple Authorized Service Provider

iPhone - Contact Support - Apple Support