Posted: 01/06/2013 at 21:16
Any idea how old the vine is? A one year old plant should be fine in a 19cm pot. In its second year move it to a 30 or 40cm pot. If it is going to live permanently in the pot then use a compost with loam (John Innis type) or add some to multipurpose compost. No need for manure though as grapes are very vigorous plants and can cope with very poor soil. Give them too rich a soil and they will just produce far more shoots than you can cope with.
Give some thought about how you are going to train the vine. It will grow large and needs to be kept under control. Useful info available on the RHS website here http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=287.