Unplanted organic seed potatoes

Hi, I am new too all this, as I just got my plot 6 months ago and have spent a lot of time just clearing some of the ground. I accidentally bought too many spuds and wasn't able to plant them. I've read alot of the message board, but have got two questions, if anyone can help me...
1) The potatoes I havn't planted ( because I had too many) have got long sprouts on them ( I think I kept them too warm in the house). Someone advised me to snap the sprouts off and store in a sealed paper bag in the allotment shed. Is this the right thing to do and can I plant them next year - will they be ok?
2) I havn't planted my late maincrop, they are called Arran Victory and Cara. One of the forum members said you can plant as long as there is no frost - they need 20 weeks? Can I plant them now, or is it too late? I am just about to dig up the rest of my earlies which have now got blight I think and also are being eaten by slugs. I did dig up some of these a few weeks ago but it was too soon and they gave me stomach ache, but they hadn't been attacked by the slugs then! If I can plant the Arran Victory and Cara, can I plant them in the same place, or are they then just going to get blight too? I do have another patch thats free.

Thanks, please let me know if this is already on the site somewhere..

oops, havn't got a greenhouse, only a shed...
I checked the blight, I was wrong, it was just too much rain and some of the other spuds are alright. thanks

thank you very much, i think i will try to put some in my dad's greenhouse and plant some in the ground (when it's cold) and see what happens.