I couldn't find anything about Giant Russian onions, but I found this:

http://www.dailymail.co.uk/news/article-1214511/Giant-onion-green-fingered-enthusiast-crying-tears-laughter.html

Does that look like the variety, Vera?

Thank you Tugbrethil,I found the article which shows the huge onion,so it proves that it is possible to grow them as big as your head !!
I shall try my best to do just that,and if I succeed I will photograph it to show you . I intend to start the seeds off as soon as I can get through the snow to my greenhouse.
( In the small propagator )

Best of luck, Vera! I know how to grow big onions--though not that big--here in the desert, but I suspect most of my info won't transfer to your climate. The main thing I know that might help concerns soil and feeding.

The softer and better drained the soil is, the bigger the onion will grow. Quality soil is a must. All Alliums, including onions, are dependant on beneficial fungi called "mycorrhizae", so you might want to look for a plant starter with these in it. Glomus species are very important, especially G. mosseae.

Onions need a constant, moderate supply of nitrogen and potash. A certain minimum amount of phosphate is also needed, but large doses won't enlarge the bulb, and might cause it to bloom early! Timed release and/or organic fertilizers can provide those nutrients in a manner that doesn't involve mixing and pouring every week, with worries about forgetting--or double-dosing!

Hope that helps!
Tug

Well ! it was all for nothing !
I took great care but not a single seed of the huge variety germinated.

I ended up buying sets,and also sowed other seeds ( Wellingtons).
Now in the middle of May and now transfered into permanant positions,from the cells they started life in,so hoping for the best.

But how I would just love to grow those huge ,big as your head ones !!

Thanks Tug for your advice,

Drat! Sometimes you get the onion... : )
Tricks for onion seed germination--some of which you probably already know:
Don't plant too deep. Onion seeds are tiny, and shouldn't be more than 4 mm underground.
Avoid crusting. Covering them with coarse grit is better than covering them with soil-based or peat-based compost.
Avoid drying out or washing out. I would start with moist compost, then water them with a coarse mist twice a day, until the seedlings are coming up, then gradually water more heavily, and less often. They can be started in a propagator or under a dome, but you should inspect every day, and remove the lid as soon as you see green. Otherwise, you will need to go through a painstaking hardening off process.
Keep your cool. Onions are primarily Mediterranean plants, and germinate best at moderately low temps--10º C to 18º C.
I hope all this helps next year! "Bad seeds" are fairly rare, especially from a reliable supplier, but are still a possibility, too.