I will try with seed compost and then if it goes wrong again I will buy some root trainer cells to see if it is the depth of compost that is the problem.This happened to me last year aswell but I am new to growing my own so I put it down to not knowing what I was doing,obviously learnt nothing in a year!!
I use disposable plastic drinking cups and 3/4 fill with general purpose composting soil. 1 seed per tub. Water a little,frequently,keep in the green house. No problems. Have just planted out into their final postions.
Why use a seed tray then a pot and then into their final postion.
Least disturbance for any plant is better!!
I know you use more composting soil but it does get the results you want.
Thanks for all your replys,I have planted some more seeds into cardboard toilet roll middles then I can plant them with no root disturbance at all as they will break down in the soil.
Thanks again Keith.