No quite an Allotment, but advice on my veg plot please

Hi Guys - not sure if I put this here or not - anyway - here's a plan of my little veg plot. Last year only saw a whole load of weeds, as everything got munched by the slugs, after being burnt & lashed by the wind, then trampled into the soil by the rain....
So - advice please - what do you think? Are the groupings ok? Is there anything else I should try & fit in? I have a shady bed outside the kitchen door which I like to try & grow herbs in & sun loving ones go in pots on the patio.
I have a greenhouse for the toms, cues, chillies & peppers.
Thank you

 

It looks ok to me but crop rotation is very important have you taken this into consideration?

 

Agree on crop rotation, risk from mixing Carrots with Onions (that next year you will also mix them, rather than keeping them separate and rotating them round the beds).

Sprouting Broccoli is a large plant. I think you will struggle to get one in with a Courgette in (what I think is?) a 3ft gap.

I wonder if it is worth growing Onions in a small plot? I love the onions we grow, so can see the sense in it, just that with a small plot I would concentrate on the crops that

a) Cost the most in the shops
b) Have better flavour if picked fresh, rather than being a couple of days old in the shops
c) Crops where I wanted specific varieties, not available in the shops.
d) I suppose things that I wanted to be able to pick there-and-then - courgettes probably fit that bill, as would herbs.

 

Thanks for the comments
Yes -Have thought about rotation, but have a jiggle around. The only Brassicas I am likey to grow are Sprouting Brocilli.
I am only growing onions as I was sent 40 freebie sets. Otherwise I wouldnt bother - lets take them out.(anyone want 40 onion sets???)
Perhaps I should put the Brocolli where the leek are and take the carrots out the onion bed.
What group do Courgettes come under?
see revised lay-out:

 

Honey Bee, don't forget about companion planting just to complicate things further!

http://en.wikipedia.org/wiki/List_of_companion_plants

 

Yes - have some marigold seeds I harvested from last year, and was going to put some Nasturtiums around the edge, and of course there (hopefully) will be a whole host of flowers along the edge in the wildflower border by the pond.
Oooooh! - looking at your link, nFrost, I may have to put some Zinnias in by the beans!

I have also found a manky old packet of sugar snap peas, so if any germinate, they will have to be sqeezed in too.........
All I need now is a nice buff man(cough) preferably muscley & scantily dressed (NO builders bottoms (Husband!!)) to dig over my veg patch for me........ in my dreams!!! Oh - and some sunshine..... Now, which one of those two is more likey???