Growing container grapes (cut back to stump method)

[sb329]

I've just got myself a fairly roomy greenhouse (8x6' with 8' to the apex) so would like to try my hand at growing dessert grapes. (I'm in South-East UK and inexperienced with growing fruit and veg) Initially I was going to plant the vine outside and train it into the greenhouse as this seems to be the most recommended method, but a bit 'eggs in one basket' if it goes wrong.

Then I stumbled on a 'foolproof' method where you plant in a container, and the canes grow vertically up a 6' support to fruit, and at the end of the year you cut them back close to the rootstock and move the containers outside for winter which helps kill off any disease. This also means the vines are much more compact, so I went all-in and bought three varieties, they are about 50cm tall at the moment.

As this removes any requirement for training the vines along supports, I'm not sure what to do for the first year as most guides assume you are training the vine;

• As they grow up the supports does it matter how many canes I allow?
• Should I remove and discard any grapes or let them ripen? (Will this benefit the vine next year considering I'll be cutting everything back?)

If this venture is successful I think eventually my favourite will be planted outside and trained into the greenhouse to increase the quantity of grapes, and if the others are still healthy I might train one of the others as a 'standard' and see how it does outside in a larger permanent container.

Thanks for any tips.