Back in March I asked about using "seed compost" rather than general
purpose for sewing seeds in.

I have just potted my tomatoes (Sun Gold) in to 10 inch pots today.
They are the sturdiest and "rootiest" that I have ever had.
This year for the first time I started the seeds - and then repotted
in to 3 inch post with "seed compost" rather than general purpose.
I guess this is what has made a very big difference - thanks to those
that recommended doing so.