Grapes in a polytunnel?

[Odsox]

how much do trim back or do you just let it have it's way

I trim each lateral to one leaf after the last bunch of grapes.
Then just keep an eye out for side shoots that try and make a mad dash for freedom.

Out of interest, when do you pick your grapes ?
It would interest me to know just how much further south my greenhouse puts me compared to outside.

[cherami]

The new grapes in the Tunnel I hope to be in September time, but cannot be certain, the grapes in the vineyard are about the sept time depending on weather. It's hard for me as a none expert to say what kind of grapes are in the vineyard, I know it was established in 1923, one is a Pinot for sure, but what kind of Pinot I am unsure. I have a good book on Grapes by Alan Rowe.

[Odsox]

Thanks for that.
I didn't make a note of when I started picking my grapes last year, but I did note that I stripped the remainder to make wine on the 17th of September.
So that places my greenhouse several hundred miles south to central France without the expense of air fares to pick them.

[Odsox]

I can now answer the original question (and correct my original reply as well)
This summer has been the wettest, coldest and most humid since I've been polytunnel growing, and now that the tunnel black grapes are ripe I can report that they are not suffering in any way, mould or otherwise.
Also I'm rather impressed with this variety, as despite the lack of sun they are sweet with a lovely perfumed flavour, unlike the white ones in the greenhouse which are still a bit on the sour side.
As it's the first year fruiting there are only a few small bunches, but next year I should have enough to dry as well as eat fresh.