Not sure what you mean by 'containers', Mike. Are these pots, boxes, troughs? Whatever they are, 9 inches wide is pretty small for any vegetables unless they are also long and deep. You don't say where in the UK you live but in my area (Somerset) the runner beans are already at the top of their supports and cropping so you have started very late to think about them. Leeks are essentially a winter crop and runner beans a summer one so you could grow them in the same place but that would only be if there is plenty of space. You say you 'believe' that leeks can grow quite big. I suggest you go to the nearest greengrocers and look at some! Are you wanting baby leeks or the big fat winter ones? If the latter you are looking at a period of about 10 months plus from seed to crop, a long time to be waiting if you have limited space. Also get yourself a good vegetable growing book, like the RHS 'Vegetable garden displayed' by Joy Larkcom. You sound as if you've started growing stuff without looking into it first. Runner beans are good in containers as they are pretty and crop over a long period but they do need deep rich soil. Leeks I would think are not really worth it as you have to wait so long for a crop and as soon as it is ready you harvest it and your display is gone. Tomatoes and peppers are good value in pots as are cut and come again salads and herbs.

Flora,
I live in the new forest (Hampshire), not far from your neck of the woods. I am growing in pots and no 9 inches isnt a lot but id imagine big enough to grow single leeks in. I didnt actually plan to buy the beans, I went to buy some other stuff from a garden nursery and had another impulse buy, which seems to be happening very regularly at the moment, its so addictive. I could grow the runners in my raised beds but these are in the shade and although they get light all the time they dont get any direct sunshine. However may I add to this point that the broccoli and cabbage plants seem to be growing very well here.
Latly in response to your suggestion about cucumbers and tomatoes. I have about 50 (maybe more) tomato plants and 36 cucumber plants at the moment and about 20-30 bell perppers, all of which are grown in grow bags and pots.
I am stuck as to what to do with these runner beans. It may just be a case of sticking them in the shade purely as an experiment.

They may well be fine in the shade. They'll probably grow taller and with the flowers further apart (etiolation) but it's worth a try. Whatever you do, plant them quick. My brother has been picking for two weeks in Romsey. Are you going into the greengrocery business? 50 tomato plants???? There are four of us and I grow 12 plants outdoors. If I had a greenhouse I'd also put in another 12 indoors.

Sounds to me as if your autumn project should be to dig yourself over a decent sized vegetable garden - you seem to have caught the bug badly.

I live in lymington probably about 30-40 minutes from Romsey and there arent many beans being picked around here at all, not from what Ive seen anyway.
Bean plants have only just started flowering.