Wisteria frutescens is a tough, hardy plant, that is usually pretty easy to bring into bloom. On the other hand, it does like good drainage! If you can't find another spot for it, or correct the drainage problem, a pot may be your only alternative. It will need a large pot--at least 70 cm tall and wide--and a sturdy trellis, or wrought iron "umbrella", to climb on. Keep it well watered during the summer, and feed it regularly with any balanced plant food. It may also be a good idea to wrap the tub in bubble wrap in the winter, to keep the soil from freezing all the way through.
By the way, that one doesn't look like the ones that I have raised--it looks more like a W. sinensis. I hope it came from a good supplier.

And you wont be able to just have one stem so that it looks like a tree.

That's not strictly true, MG - training advice for wisteria is to allow one, two or three vertical main stems and remove anything else, let it get as tall as you want, then cut the top out to force lateral growth, so its certainly possible, with rigorous attention, to only have one main stem. I have a friend who grew one like this in her front garden up a 2 x 2 solid wood post, looked like a weeping tree.

I stand corrected, the only wisteria I've seen have been growing up house walls.

Thanks for your comments:
Tugbrethil: This bought for me by a friend who knew I was disappointed with my w.sinensis alba (which got chopped down last week, I was fed up pruning and waiting to see, the last straw was a late frost that killed of all the leaves and what I thought were buds). As far as I am aware it was bought via an article in an RHS Magazine which featured Wisteria, so I can only presumme it was reputable. It would cost me thousands to fix drainage. My neighbours are far worse than mine and it drains pretty quickly once the rain stops.
Bamboo: That was the kind of thing the article was about - training them as trees. I wasn't expecting it to be this small. The last time I bought my wisteria it was much bigger.
MG: I was under the same impression until she showed me the article. They were grown in the ground but article said they could also be grown in pots.
Do I leave it in this pot until next year or do I put it into the next size up or the intended size of 70cms?
I have John Innes No1 (left over from repotting the geraniums, Bamboo!) would that do or mix it with something else?
Thanks again x

If its got plenty of roots coiled around, repot now into a pot twice the size of that one, using some John Innes No. 1 and multi purpose (really, you need JI No. 2 or 3, No. 1's for seeds and cuttings). Keep checking as the season progresses - once it starts growing you might find it needs potting on again before autumn. If you're not growing it up a support on, say, a fence or wall, then you'll need a large, solid stake of the height you want the plant to be - the problem with that is, how are you doing to fix it in a container, specially while you're still moving it up in sizes, dunno what the answer is to that one. You've got a bit of a problem with training too, because the main stem is short and doesn't look as if its going to grow from the top any more, so select one of the new shoots to become the central one and remove all others till that shoot has thickened up and got to the height you want, then cut it. You can remove small buds and shoots off the stem by rubbing them out before they open, and clipping off larger ones right where they emerge from the woody part. Because you're starting with a short plant, it's going to take longer to train I'm afraid.

Good luck Scottish!

Thanks everyone....Bamboo, I will get some No2 or 3 at the end of the week and do this properly. I need to sit down and think about the staking of it. Your help is most appreciated.
Fingers crossed everyone!!!!

I don't envy you the dedication and commitment this project will require, hope you've got enough time...