Re the plants: We don't have the space for one, but I find most perennials overwinter well repotted in larger pots.

Oh, yes. I have two holding beds as well as use my vegetable bed to overwinter plants. Most of the plants in the holding beds are from winter sowing and need to grow on before I give them away or find a place for them in my garden. Some are from fall sales last year and waiting for me to finish their new bed this weekend. Some of the winter sowing plants are ones that I want to see blooming or more mature before I decide if they will be kept.

I do it. I have an old kiddie pool - the rigid plastic kind that I put drainage holes in. I use it to put things that people give me where the color might be unknown, or when I buy a lot of stuff on sale this time of year that I don't have a definite home for. I wish I had done this from the very beginning. It would have saved much moving around of plants. I also plant my garlic in there - so I can find it again when its time to harvest.

Skibby

I have a vegetable garden that works great as a nursery bed. I find more and more that fresh veggies aren't really my thing so most get given away anyhow.
I like lettuce but I like having room for rows of hellebore seedlings more...

Any excess winter sown perennials used to get set down in trenches that I then filled in with garden soil so the plants sort of simulated being planted for the winter. I never lost any that road. Winter sown shrubs/trees just get planted in large containers and spend the winter on my east/west facing breezeway. Most are winter hardy and all have survived since 2010. Heads up--many mail order/nursery-grown plants don't make it, I'm guessing because they're grown in greenhouses. Winter sown plants are much more hardy.

I usually leave plants waiting to be planted along a section of fence that leaves them in shade most of the day and keep them watered until I can get them in the ground. If I still haven't got them in the ground by Fall, I have dug them into the raised vegetable beds, pots and all and covered with chopped leaves for the winter. This has worked surprisingly well. I don't have the room for a bed dedicated to holding plants either, and I'd rather plant them where they are going for the most part and just give them extra care in that placement.