Successional Planting ~ how do you make the most of your plot?

I think it's too late for leeks to be sown for this year - though others may know better.

Not sure about many of the other specific questions, but you may find the Monthly guides, and the Seed Sowing / Harvesting chart, of some use in planning when to do what - click the Growing Help link near the top of the page for the index page.

Or treat yourself to John's book (on the main Home page of the site) on Vegetable Growing Month by Month 

P.S. Don't forget that it can sometimes benefit the plot to have a short fallow period rather than permanent cropping of one sort or another.  You don't want to exhaust the soil.

You'd best get a move on with your leeks   they be transplanted into the bed when you take new potatoes out they probably won't make huge ones as it is a bit late.
winter cabbage to be sown may/june according to my pkts and transplant when big enough to handle (4 or 5 leaves stage) depends when you plant them how late you can leave them
Autumn king carrots can be sown in August.

Autumn king carrots can be sown in August.

Think that's a little late, MOS - my packet says May to June.

I'll have a shot at answering the Subject, rather than the specific content

I think there are two approaches - a nice row of Cauliflower that look very smart - but then all come ready at the same time causing glut - which either results in a massive freezer-filling session (you might as well buy them from the supermarket IMHO) or a pile of blown Cauliflowers on the compost heap

Cauliflowers (to use that as an example) typically only have about14 days from ready-to-bust We eat one or two a week, so I sow 4 every fortnight. I grow them in small pots, and then plant out. I never have a smart looking row, but rather an oddment assortment of this & that.

Careful notes from previous years of "did this then" and "that happened on such-and-such a date" enable me to do a little & often approach - but even so Real Life and Work gets in the way - so my fortnightly planting becomes a month, or six weeks, between planting

So ... my approach is clearly just for Nerds like me then! But choose your poison depending on your personality.

I would venture to suggest that my pedantic, grow-everything-in-pots approach is not dramatically different to sowing direct in the ground.

I have more fiddly sowing, pricking-out and transplanting, for sure.

But on the up side:

I don't have to have the seed bed ready early in the season (difficult on my clay soil)
I am sure how many plants I have (failure of seeds sown direct in the bed represent a very late "replacement crop")
I have no gaps in my plantings - whereas seed sown direct will be too thick, or too thin, but rarely "just right"

Horses-for-courses though, and ask two gardeners and you'll get three opinions!

raising all your plants in pots has the disadvantage of having to buy extra compost and may be too costly for those on a tight budget.
Little and often is a good way to go though, unless it's peas and then plant as many as possible  

Good point about compost cost (although I justify it as "soil-enrichment" )

Well I've learnt that instead of sowing two by one yard rows of salad leaves, I should sow a foot/18 inches, leave it ten days and do the same and so on. I am now eating fresh mixed salad leaves in sandwiches every lunchtime which is no effort but I still have a yard and a half to go!! I'll look lime mizuna soon!!