DIY potato containers - some advice please.

[Willonthewall]

Next year I fancy trying some potatoes. I'm thinking of Mayan Gold or Mayan Queen from Thompson and Morgan. My question for you experenced potao growers is this.
I have access to pallets and I fancied making some 2'-0" cube containers with a removable glass top. I can bed the seed potatoes on about 4" of compost/soil mix,cover with a few more inches, and gradually top up the level as they sprout till I'm almost at the top of the container.
1 - Will that size be adequate and if so, how many tubers will I plant?
2 - If it needs to be bigger I want to keep the top 2 feet square to use spare horticultural glass so how deep would they need to be?
3 - If I use temporary insulation for the outside and use the glass covers, how early can I plant bearing in mind I'm in Northumberland?
4 - Will it be worth the extra effort in making "trapdoors" near the bottom to remove the crops as I want them, or should I just wait till I know they're ready and just empty the containers? Trapdoors will mean quite a bit of extra strengthening to make sure the thing doesn't collapse when I open one.