Potatoes Please

[OnlyWantsOne]

Brought some maincrop seed potatoe things (havent done this before) and instead of the grow bag type things for spuds, bought two large plastic tubs for them.

Instruct, what do I do, how deep as the tubs are about 2 feet deep?

out a layer of compost in the bottom, put the spuds in, and put a bit more compost on top. As they grow keep adding compost (like heaping up with ones in a conventional bed).

but how many layers can I bung on top of them, my pots are two feet deep, if I say, put the first potatoes on 4 inches or so of compost, that leaves a lot of growing to do before they are allowed to actually leaf up without me mounding more compost on them?

I think you can probably keep mounding them up until they don't look happy.

Apparently you let them grow to about 6 inches above the soil, then put 2-3 inches more soil, and carry on doing that, til you get near the top of the tub.

I have heard of people growing them in half barrels.

you don't wait until the leaves are 'out of the pot', Just about 6 to 8 inches of plant leaves, then earth up , and continue on until you are at the top.

and they'll go all the way to the top?

They are about the size of half barrels actually

Whats the best compost / soil?

I am not filling them up with John Innes number 3 like the girl at the garden centre told me to

Yes, they will get to the top - I planted mine in the same things about 6 weeks ago and they are nearly at the top now. I've heaped up soil on them about 3 times. Make sure that you give them plenty of water.
I've just been using some stuff from an old grow bag with some fertiliser mixed in.

How big do the little shoots have to be when I first plant them?

They are currently about 1cm - 2cm

That'll be fine.