Move them when the roots are visible coming out from the bottom of the tray/pot. When planting in the garden I would also scatter slug pellets to protect them as they are caviar for slugs and snails
It could be Bay sucker, the damaged areas dry up and turn brown. Leaves may also curl up. You may find small nymphs on the underside of the leaves. There is no cure, just remove the affected leaves.
I think it's a Kerria Japonica
It could be a Campanula, bellflower.
I had 14 frogs in my pond earlier today and first spawn recorded. I'm in northHampshire
The grass one looks more like a reed than grass.
If they have been stored somewhere dry they should be OK. If they have spent the winter wet it's possible that any nutrients in them will have washed out so not much good for growing plants on but great as a mulch for the garden
Cornus and Salix would give add winter colour and both will tolerate clay and shade
I use soil taken from my veg patch mixed with homemade compost to fill my bags. I generally put 5 first early tubers in each bag. One year I initially part filled the bags and then 'earthed up' by adding more compost as the stems grew. Second year I put all the compost in at once and buried the potatoes at about 18". There didn't seem to be any difference in the final crop. I start mine off towards the end of March and feed with tomato feed from May onwards.
There is a porous hose on the market which I have had some success watering a difficult to reach flower border. You bury it about half an inch below the surface. I'm not sure if it would be able to provide the amount of water vegetables need to grow well