I'm guessing they don't really dry out in Wales with all the rain :L

 yeh its amazing clay really stick, there mostly in the shade, so they dry out very slowly so we dont get any cracks, we cover the ones in the sun with tarps when we're not there to stop them dring out.

 Must be some level of sand in there or it would be really hard to work with? We have some clay around these parts but it is mostly the blue super fine stuff which is great for brick and roof-tile but too hard and sticky for building from.

 yeh it changes depending where i dig from, sometimes there is some sand or silt in it, but the dirt for this feature was very sticky, I had to wet the spade after every other stroke to stop it sticking.

 Looks that way yeah
This time of year it rains a lot around here so the dirt I'm currently building from is extremely heavy. A days work and I'm pretty spent from wheelbarrowing and digging, hehe.
Anyways - your spot looks real nice & probably going to be awesome once it dries up in spring.