No, definitely not the Bluetits.

This last cold winter is a possible candidate as Clematis montana can get damaged in very cold winters. It will try and make up the damage in the growing season with growth at the expense of flowers. It should be fine hopefully next year.

Thanks Fractal. Much appreciated. I shall stop worrying, in that case!

Sorry to hear your Montana was a dissapointment to you this year Rob.as mine was the best its been yet. Mine was absolutely loaded with flowers. I will see if I have posted any pics ,if not I will look for one to post. Yours should be OK next year , these are quite tough plants.