Signing up is as much a way of showing support as anything else if you do it anyway really.
I do like Plantlife, they do some really good work.
Sowing a wild flower meadow isn’t always as easy as it sounds, I’m sure a lot of people get put off when things don’t grow.
I tend to go for plug plants rather than seeds for most things & just look to see what grows locally too, I know I’m never going to have a lovely garden of red poppies as they hate all the rain so you have to find the right plants for the right place.
I’m not sure how celandines spread but they do spread like mad! There’s quite a lot growing by streams & rivers or just damp woodland here, I picked mine by the side of the road years ago & they’re all over the garden now, I know some people don’t like that but they don’t last long before they disappear completely leaves & all until the next year.