Tracey I grow in bags see Garden photos 2014.
I planted 3 chitted spuds to a bag, planted in multi purpose with some organic potato feed, have used Growmore in the past.
In a cut off bin I'd plant 6. Need plenty of water as they grow and keep topping (mounding up) up to cover new growth, spuds that grow need to be in the dark.
Seems a lot of compost but you can chuck on garden afterwards.
Not too late at all, I usually do at Easter (ish) but have done early due to weather. I chit mine, but I understand it isn't vital. I only grow 1st & this year 2nd earliers, don't bother with main crop. Just about finished the spuds I grew last year, they are in a paper sack in garage and still taste good.
If you need more info' shout