[Eblana]

I planted some basil seed yesterday in modules but the seed was small so I put about 4 or 5 seeds in each module.  If/When they germinate should I leave them as is with 4 or 5 plants in each module or should I prick them out into individuals.  I want to plant them in the border in the PT under my tomatoes.

[DD.]

Blimey, you've got more patience than I have with sowing leeks.

I sow mine in a seed tray then transplant in clumps to other seed trays, grow on and plant out.

[GrannieAnnie]

Ditto! 

[RichardA]

I have done that ( 2 or 3 seeds per module) with basil as well as by the seed tray and then plant as clump method and also by sowing direct into ground thinly. Leaving 2 or 3 as a clump is no problem. Growing close to tomatoes is a good idea - seems to deter whitefly a little ( I find tagentes is much better) but also my OH knows where to find basil come the tomato soup etc season starting. So go for it.
R