I usually sow them directly in the ground where they are to grow. I find pre sown ones are more likely to bolt due to root disturbance when they are planted out.
more went to seed quickly last year due to the erratic watering.

Just like Eileen, I used to grow my beetroot directly in the soil so no root disturbance. I would do the same and wait until it warms up so there is no check in the growth. They don't look out of place sown in between bedding plants.

Thanks, both of you! The thing is, I don't have a lot of space and sometimes grow them in quite deep troughs. I get about four in them.