For now, just deadhead them... you should be able to get several more weeks of blooms out of them. Our's, here in the U.S., started blooming about two weeks ago and are doing well, but I expect our growing season is a month or so behind yours.
As to pruining...it depends on the varietal. Yours could be a Type 1 or 2 (sometimes references include Type A, B or C). I suspect it's a Type 2, which begins blooming in mid-May until about now. They bloom mid to late May and if healthy will repeat bloom in September into October. These flower on both old and new wood. Prune lightly in spring when buds begin to swell, removing dead and weak stems and reducing size if needed. The largest flowers will be produced on the old wood while new growth will provide bloom for late season. Group 2 can be pruned again immediately after flowering if needed. (
Source University of Illinois Home Extension).
If you happen to know the name of your clematis you can look it up for the Type that it reperesents... Perhaps here:
http://plants.usda.gov/java/ClassificationServ let?source=display&classid=CLEMA ... Best of luck!