how many seeds to sow for 6 brussels sprout plants

Just getting started this year, i have made up a seed bed ,prepared most of my vegtable plot .I am starting to think about sowing my brussels sprouts, broccoli and leeks but theres about 250 in each seed packet    i would like 6 brussels 6 broccoli and 4x 4 1/2 ft rows of leeks ,if anybody could tell me roughly how big my seed bed rows need to be that would be brillant
cheers Ian

we plant our sprouts at 2ft apart

and right in as far as the 1st set of leaves ,

then we protect with debris netting untill thay are a foot hight ,

Hi Jamie, I'm new to vegetable growing too. I've found John's vegetable growing guides really useful, especially the one on sprouts. Have a look at this page and scroll down till you come to the sprouts article.

http://www.allotment-garden.org/vegetable/index.php