[Lee G]

How thirsty are they, it's my first attempt and after building a lovely frame with debris netting to protect them I don't want to lose them through lack of water or indeed too much.

[sunshineband]

I water mine while they are recovering from being transplanted, and then give them a good soak once a week if the weather is really dry (like this week)  ie a couple of gallons per sqaure metre. I try to avoid getting the leaves wet. As brassicas are grown for leaves I reckon they shouldn't dry out, so might up this watering to twice a week if the weather is baking 

 Others will have advice too -- be interested to see what they do, too 

[Bozwell]

I think it's a good idea not to let them dry out too much especialy while they are young seedlings. I bet a lack of water will make them more prone to bolt.

[Salmo]

Puddle them in when you transplant them and give them a little water until the leaves do not wilt in the daytime any more. After that be quite mean with the water so that they have to put roots down. If you water too often the roots will only be shallow and you will need to keep watering the whole Summer.

[Kristen]

I puddle in too, and water once a week (unless there has been an inch of rain, or so, during the week).  I water the plant, rather than the whole bed, and give each about a litre I guess - so the water soaks down to the roots, rather than just wetting the surface.