Thanks everyone for your input. I've been looking at images and reading up on Echium vulgare and like nutcutlet, I'm confused. The plant I have bears no resemblance to vipers bugloss, not in size, stem, nor leaf. And the flowers are quite different.
And as nutcutlet points out, if it's a dwarf hybrid, what plant is it hybridized with? I can find no reference on the internet to this hybrid, apart from the blog page mentioned by dovefromabove and a company selling seeds for it.
I took some better pictures this morning and one thing is very noteworthy and that is that the flowers are less in number and further apart than vipers bugloss and emerge from the stem with a basal rosette of 3 small lanceolate leaves that are unlike the main leaf of the plant. At the moment the plant is 26cm tall.
The second and third pic's clearly show the lanceolate leaves at the base of the flower.