Yep. I got one.
If you are an EE customer, you can get one and use it, then take it back to the shop and exchange it for a charged one - useful if you are touring. If you're not a customer, you can still get one (and do the exchange thing) for £20.
My wife has a different type in her car, it runs off AA batteries, which is probably a little more useful if you've no power and only a small shop to get supplies from.
I've tried some of the solar power banks to, the cheap ones aren't up to much, not sure about the expensive ones.