I use 4litre pots often called tomato pots at the garden centres. They are about the size of a typical household bucket.

good roots produce good crops beverley so here,s my method for success. i dont use growbags, I use an old plastic washing bowl into which i put 6 inch of soil. Then i use a bottomless tomatoe pot (Very cheap at your gardenshop) place this on the soil in the bowl. Fill pot and put tomatoe plant in it. Water top of plant once(should be 1 inch rim on pot top) then only water around soil in bowl not in pot. Feed plant via top of pot only. Large crops are on the way to you. Take care enjoy.

if you go to your local morrisons they usually sell of their buckets what they sell their flowers in for 99p you get about 10 to 12 buckets for that price i know my local morrisons do it.
Then all i have to do is drill about 3 holes in the bottom of the bucket , several of my plants live quite well in them