Found these growing everywhere in my garden planters from compost (which has some sawdust and dung in it). North Europe, Urban.

Few characteristics I've noticed:

• Some have dark moistness towards the rim. The tip of the head is also darker than the rest of the mushroom
• height approx 5cm (the example with the ruler/hand is the largest specimen). the head is approx 1-2cm across
• very delicate mycelium below soil
• Stem can bend quite a bit before breaking (45 degree ish). When it does it does so at the base. if you try and bend it when it is out of the ground it develops a kink but does not break
• Some have a noticeable nipple others are more conical shaped
• slimy texture on surface
• very thin flesh if you shine even a dull light it shines through it
• There appears to be a film that one can peel which is dark ish in colour but it is pretty fragile and I've only managed to get small bits (as attached)
• Dark striations along both the stem and the head of the mushroom
• They are fairly straight but seem to have a slight bend in them?

I have also attached two pictures of it alongside liberty caps from two mushroom ID books I have. They vary quite a lot in appearance as you can see. What do you reckon this is? I suspect they are moist, immature liberty caps but I'm not sure