At this time of year, the ground can still be too cold to sow seeds direct. The answer is to sow under cover or in a greenhouse if you have one. You can even use a windowsill in the house that does not get long periods of strong sunlight or the seeds may overheat. Facing east or west is best. But even that might not be warm enough for things like tomatoes and courgettes. The answer is to use either a small heated propagator or a heat mat under seed trays.
Seeds vary and need different temperatures for optimum germination. A partial list of temperature can be found here
The photo shows trays of tomatoes, courgettes and strawberry seeds shown on 22 March. They will each germinate at different times and will need pricking out into small pots in a few weeks.
This is a “Trio Top Electric Windowsill Propagator” from Kings Seeds. There are other makes. It is also worth checking out our local Derbyshire suppler Two Wests & Elliot The usual disclaimer, I have no connection with either company other than as a customer.
Look out for updates as the seeds germinate and information about what to do next.