Clematis

I have a clematis which flowers during March and April; it was here in the garden when we recently moved in; I'm unsure when to prune and whether i should prune lightly or take it back to the ground. Its currently a good 7ft high and looks as though it hasnt been pruned in a good 5 years or so and I'm worried about making a mistake with it.  Can someone help? 

Simple rule about Clematis pruning. Flower before June, don't prune.

So, to modify it, after flowering remove any damaged, unwanted shoots, dead bits and finished flowers.

Post a picture on a Forum and somwone will be able to id it for you I am sure.