Im growing Minibel tomato plants and I use a 6inch pot for each of them , I also had a couple in hanging baskets last year and they grew well , have a look at this site , Nick runs it and he is so helpful if you want to contact him about anything
http://www.tomatogrowing.co.uk

I grow 'Gardeners' Delight' - one per large pot in the greenhouse. I tried more outside last year, but they all succumbed to blight! I am sticking to my greenhouse this year.

I did cherry toms outside last year - 1 per basket like Weemamma says. While not heavily fruiting, I got quite a few - better than the greenhouse types (due to the lousy weather). You could try some outdoors, and some indoors.

Yes you can and an old wine barrel is perfect! This is what mine looks like:
http://media.growsonyou.com/photos/photo/image/93399/main/DSC05508.jpg

Here is today's harvest:
http://media.growsonyou.com/photos/photo/image/93400/main/DSC05509.jpg