It's a great time of year for planting them. There are still plenty of flowers left to identify the plant if you can't recognise it, but also plenty of dried little seed cases. Of course once you get familiar with the plant you can return and get more seeds even if there are no flowers left.
The wild poppy variety here in Reading is more flame coloured than the true red as in the nicked picture above. I've been pinching dried seed cases off and throwing them into my bag. I then sow the seeds in weedy areas that could use a little colour. So far I've done one neglected churchyard, part of the canal path on my way to work, and the edges of the pavements through a second churchyard.
Can't wait to see if they take next year. Poppies are very scrappy plants. Some of the ones I harvested seeds from are growing in the barest sliver of soil in the edges of a road or pavement, so I have high hopes for survival rates.