Interesting about the reason for using tubes i.e to avoid root disturbance because I have tried that, and pots etc. but have returned to using ordinary seed trays with 24 seeds in each tray, simply because it is easier and quicker. The roots do entangle but if you plant out when the soil is warm...and I am sure that is critically important... then there seems little check, if any to growth. I reckon the most important thing is timing and sowing the last week of April to the beginning of May is about right, as long as you can bring them on quickly, in a warmish place. The only thing to watch with seed trays is damping off. Don't keep them too moist and either rinse the seeds in weak bleach for a minute or two or use some fungicide like copper sulphate. I have and use occasionally a gadget, probably obtainable called a soil block maker. It is a steel hexagonal open ended mould 3" across with a press handle at one end; moisten soil and ram it in, then press out a block, scratch a seed hole and Bob's your uncle. Widely used at one time by professionals, perhaps it still is.
