Many gardeners are still swayed, by advertising and easy availability, to buy commercial peat-based potting and seed composts. There is no need to do this. You can buy good commercial peat free composts such as Sylvagrow and Dalefoot, or, even better, you can make your own potting mix very easily.
Whilst some of us can use loam from mole hills, you don’t have to go out searching the fields – simply mix one third soil or your own compost, one third leaf mould (available free from BCCS) and one third horticultural grit or sand, and hey presto you’ve done it. Garden Organic has an easy to follow guide for different types of potting compost – see https://www.gardenorganic.org.uk/sites/www.gardenorganic.org.uk/files/resources/fflp/A38-Making-potting-mixes.pdf