Earthworms in soil are VERY populous eg 10,000 per square metre. They will accumulate in places where it stays damp simply because the alternative is digging further down into the soil.
I cannot tell you with absolute certainty, what type of worm there are other than Phylum Annelida I suspect they are Brandling worms, which have other common names such as Tiger worms or Trout worms. They are widespread in Europe and live on the surface of the soil, moving (for a worm) very fast. If you try holding one they have small hairlike structures on each segment (called setae or chaetae). These little bristles stop it sliding backwards when it moves. That is a fascinating process involving squeezing the segment to a smaller diameter which makes it longer, then digging the bristles in and shortening the segment the sequence gradually moves the animal forwards.
I cannot tell you with absolute certainty, what type of worm there are other than Phylum Annelida I suspect they are Brandling worms, which have other common names such as Tiger worms or Trout worms. They are widespread in Europe and live on the surface of the soil, moving (for a worm) very fast. If you try holding one they have small hairlike structures on each segment (called setae or chaetae). These little bristles stop it sliding backwards when it moves. That is a fascinating process involving squeezing the segment to a smaller diameter which makes it longer, then digging the bristles in and shortening the segment the sequence gradually moves the animal forwards.