I believe HP stands for High Performance - but don't quote me on that!
From what people have said the update seems to be more in order to use the new quilting tools to make it into the 'Quilt Maker'. I don't do a lot of quilting (I've only made 4 so far though an heirloom one is in my future using 'machine heirloom sewing techniques' and now I'm getting more into garment construction and designing my own patterns (just done a few of Suzy Ferrers classes on Craftsy (at about quarter the advertised price through offers!)) so I've moved on to other things, so it's looking more like I'll pass on the update.
I'm perfectly happy with the machine as it is - besides I have narrow feet that will work on my other machines so why reinvent the wheel. I'm quite happy with the way the embroidery works, and my needle threader is fine, so the thought of taking it in somewhere, for a tech I don't know to tinker with, is not on the top of my list! I'll need to find out who the good techs are when I get to Wales.
Thanks to those who made comments on my question.
"With all its sham, drudgery and broken dreams,
it is still a beautiful world. Be cheerful. Strive to be happy." Max Ehrmann