Thank you Nic.
Here’s a short update:
Once I could gain a look into the open nest hole as I discovered a huge entry hole in the pile that in my opinion hadn’t been there before. It looked like it has been abandoned, so I got cautiously a bit closer.. And then I saw them! Mother in her nest with two little ones underneath. Their prickles (?) same colour as mother’s. She was awake and carefully watching me. I immediately retreated and left them alone. The little family’s already exploring the garden in the night together! So they must have been born weeks before I had discovered the nest making, that in fact was just a renovation (or a house moving?).
Now I really don’t want to disturb them any more. I even think twice to pass them to reach the water barrel. Luckily, we don’t mower this patch of lawn that has changed into a meadow, but we still have to mower the rest of the lawn. It’s roughly 4 mtr. away from them. Do you think that’s possible or is it too disturbingly noisy and we should wait another 3 weeks? I read everywhere they are so easily scared. I really don’t want to chase them away.
I would appreciate your or someone else’s advice.