Who or what is nibbling their way round my garden?

I've noticed over the last week that lots of my plants are looking distinctly nibbled, and I don't remember so many plants being so widely affected in previous years. I've not seen any slugs or slug trails (and we have a family of slow worms under the cold frame who usually help out with that side of things!). I'm not even sure if it's the same problem all round or a different one on different plants!

My red cabbage seedlings - these were in the house in the propagator so someone's being very sneaky?!





And then outside, one of the clematis:





...the hellebores...





...and the daphne:



Any thoughts on who the culprit(s?) might be?

 

Red cabbage seedlings - turn that cell tray upside down and check for a slug/snail lurking underneath.

You also have aphids on them (pic 2).

 

Thanks @Scrungee - I'd looked for slugs in the compost but not underneath the pot And I wasn't sure if the aphids could have caused the completely chomped seedling before moving onto it's neighbour - they've already been soapy-watered since I took the photo so hopefully that will sort them out

 

Underneath cell trays, in the cracks between cells, especially if sitting in seed trays, is a favourite place for slugs to hide.

Aphids wont cause such extensive damage, but they'll help finish off seedlings weakend by gnawing slugs.

In case they're coming from further than under the plants, you may want to consider some slug pellets which will be out of reach of wildlife if used inside a greenhouse, etc.