I would suggest that you have started these off too early, Dave. I am not even thinking about it yet.
These seedlings are not getting enough light and are now too warm, that is why they are so leggy. I will be sowing mine in early March in the greenhouse. The seed will start off in a propagator but as soon as they have emerged they will be taken out and grown on in the un-heated greenhouse.

thanks a lot for advice BH they are unwins growsure seeds should i start again ?

Yes - in March, as Bulbaholic suggests

thanks bamboo, also have started my onions from seed and they are well on there way are they ruined ?

Normally, if your seedlings of Brassicas do get leggy like this then the answer is to pot them on, but plant them deeply, so that the bottom leaves are only just above the soil level. However, as said it is a bit early to be sowing these seeds.

No, the onions are just fine. The old gardener's advice with them was to sow on the shortest day and harvest on the longest.

thanks OB will try potting them on see how it goes

Fortunately, the stem of onions is entirely underground, so if the first leaves fall over, it isn't the end of the plant, though it will set them back, some. Note that only close cabbage relatives, monocots--such as onions, asparagus, leeks, and corn--and tomatoes can be planted deeper if they are spindly. Nearly all other plants will die if planted deeper than they were as a seedling.

thankyou all for comments