There are five widespread and common woodlouse species in the UK. This isn't one of them. Telling the species apart can take a bit of practice, and in some cases it's extremely difficult, but there are differences for those that spend time looking.

 

This is one of the species that can't really roll up into a ball (very few can do that perfectly), but makes up for it in other ways. The patterning is variable, but is normally very attractive, with marbling down the sides. For the purist who wants to check the identification, you can turn it over, and count its “lungs” (the white flaps underneath the tail). In Rathke's Woodlouse there are five pairs, but other common species that are similar have two or none.

 

The species was previously known from a broad area in southern and central England, and just crept into the extreme southeast of Wales. Turning up in Llandrindod was a bit of a surprise a couple of years ago, but it's now appeared at quite a few sites in the local area. You can find them underneath wood or stones, or deep inside grass tussocks.