Not a galanthopile, Olive, but in private do admit to likeing the little white beasties.
Snowdrops with four outer petals are unusual but do crop up quite regularly. It is quite possible that next year they might only have the three again. I have some that come up double one year and then single the following year! As for being valuable, I am afraid that this is unlikely. You could try your luck on ebay - I heard that one single bulb sold for £165 in January :-((((((

Oh there goes my dream of being a millionaire next year then!!! ah well back to the weeding and the planting and the dreaming, thanks very much for your reply.-:) -:)

Hi Olive....I bought 2 pots of Snowdrops a few weeks back, and one is a double with 4 outer petals...have a look at my pics. They are stunning but as Bulbaholic says, not that unusual.......

Thanks Janey, yep they are the same as mine, they are beautiful, love them - shame that they are not unusual we could have made a fortune eh! lol

There was a lady on the one show a few weeks back with 4 petalled ones that she was hoping would be given a variety name so she could sell them. They were in her large 'stately home/ manor house grounds. Havent heard anymore about it recently.