All three varietals of clematis can be pruned. How hard one cuts back does depend on the variety, however. If the clematis appears neglected, I would prune lightly to remove tangled growth, but not so hard as to destroy all of the old wood. Then, I would observe when it flowers to determine its variety, which would, then, be your guide for next year... Good luck!
Yes, I agree with Clanad - I'd either not prune at all this spring or just very lightly. Hope they flower well for you & that there are some nice suprises about to grow too. All the best in your new house & garden.