Grape vine pruning

[obNOXious]

Hi, I've not long moved into a very old house which has been empty some years and there is an absolutely huge grapevine here which has grown pretty wild. I'm not much of a gardener so my quesiton is how drastically should I prune it, as I'd like it to flourish but it's more like a triffid at the moment. Any advice gratefully recieved. Thanks.

[kira000]

http://www.rhs.org.uk/Advice/profiles1100/grap e_pruning.asp