Seed beets direct .....Leeks & parsnips in peat pots

From the UK:

You can cluster sow beets now and overwinter in the greenhouse - you'll get baby beet very early next year. I sow in clusters every 3-4 weeks during the growing season for a succession of baby beet, they just push each other apart.

I sow leeks in compost in a 7-inch pot in May, then when they are bursting out tip them out, separate and plant out (usually July). You can cluster sow and grow in the greenhouse now, like beet, and you'll get baby leeks early next year.

Beets: This is the first year I have grown beets. Planted in late August and now have many plants -too close together with nice looking tops. Too late to thin? Harvest when they attain size preference? Leave in the ground all winter? HELP! Thanks!

Leeks: Had leeks go to seed and now have large flower balls ready to burst with seeds. If I let these dry, and harvest seeds will that work? If they sprout out of the ground and I try to transplant them, when is best time? It tied this spring when they were about 8" tall, and they all died! What did I do wrong?