What to put in my pots & tubs?

[MissMarplesNiece]

I've got a couple of empty tubs after some of my plants didn't come out of the heatwave very well. What plants, that are attractive to pollinators, can I put in them to last through the autumn?

Is it too late to replace them with more annuals (I don't know if garden centres are still stocking these) or too early to start thinking about things like Sweet Williams/wall flowers for next spring?

From seed or buying plants?

Right now I'd buy dahlias as plants - will continue to flower until first frost.

Our local garden centres still have loads of annuals, and some are half price now.