plant identification for a comfrey lookalike

This is a plant that had popped up in the front weedy square. The leaves looked and felt a bit like comfrey, so I kept it and replanted it in another spot, hoping that I could identify the plant properly if and when it flowers. It's flowering now, but I'm still not entirely sure what it is. On the shortlist is:

- Pentaglottis sempervirens (green alkanet), but this plant's leaves aren't as spiky, and the centre of the flower isn't white. 
- Cynoglossum virginianum (wild comfrey), but the leaves of the flowering stem don't cup around the stem. 

To be continued... here. Spoiler alert: it's a Cynoglossum amabile, a.k.a. Chinese Forget-Me-Not.