Am I too late to plant carrot, peas, runners and swede from seed?
Planting Veggie Seeds
When you can plant vegetables is determined by the kind of veggie as well as the variety, and also by the hardiness zone you live in, which tells you the average date for first frost. Here's an article on when to plant: https://www.gardeningknowhow.com/edible/vegetables/vgen/when-to-plant-your-vegetable-garden.htm
You can learn about your hardiness zone here https://www.gardeningknowhow.com/planting-zones/usda-planting-zone-map.htm
or if you are in the UK (there are Portsmouths in US and UK) http://www.trebrown.com/hrdzone.html