Q.poppies have finished flowering
When my poppies have finished flowering in July, can I cut off the poppy heads or should I leave them for a while? They start to look very untidy and I’m not sure how long I should leave them before cutting them back.

Poppies are beautiful when in bloom and then the garden beds tend to look untidy and empty when they finish flowering.
Some people plant some additional perennials in the beds to fill in for the rest of the season. This works well to companion plant with the poppies.
You can leave the seed heads attached to allow more seeding, or remove them.
As the plants wilt down they also can be just left, but you can also clean up the wilted leaves if you like.
https://www.gardeningknowhow.com/ornamental/flowers/poppy/growing-poppy-flowers.htm