Grapes and mould problems

Hello, I have been growing a grape vine(black hamburg) in my green house for five years. It is rooted through an open bottom tub into the soil. Last year the leaves and grapes became covered in a grey powdery mildew. I put this down high humidity through por ventilation. I cut and burnt all the shoots leaves and grapes. Was meticulus with the winter cleaning, Jeyes fluid etc. Have ventilated properly this year but the mildew has reapeared.
Is there a safe fungicide I can spray, bearing in mind i want to eat the grapes. How do i prevent a reacurrance?

Many thanks

John

Many thanks, will follow suit next season , for the moment i have cut off all the grapes then sprayed the leaves with a systemic fungicde. Hoping that this way some curative action will take place during the rest of this season.

John

That's so kind. Many thanks

John

PS we are frequent visitors to Spain are your grapes at all close to Calpe?

Normally its Bordeux mixture thats used in French vineyards (& on tomatoes, etc). The application rate for vines is 20 gm/litre.
Im not at all sure about using straight copper sulphate: I would imagine that its more acidic. 
The Bordeaux mixture is made by mixing slaked quicklime with copper sulphate (about half and half, I think) - you should be able to find the recipe on the web.