I'm sorry the photos aren't very good and although my hands are quite red and sore they're not as bad as they seem in the pictures.
These blisters or hives suddenly appeared yesterday evening and I'm assuming must have been caused by something I brushed against or grabbed on my walk on Sunday. I didn't go anywhere I haven't been before [Derwent Edge and Win Hill] and didn't notice any unusual plants...but obviously I've had an allergic reaction to something that grows in these areas. At the moment they're not particularly painful; it just feels like a slight nettle sting or a very minor burn.
I'm posting the details online on forums and Facebook pages of which I'm a member and hope that someone may possibly be able to suggest what I might have encountered...and how best to care for my hands right now.