Passion Flower

Not sure what you mean by "no flowers" inside - the bud is a single flower which opens out flat - what are you seeing when the bud opens, exactly?

Hi Bamboo - When the bud opens there is nothing there only the outside /inside of bud, if you can understand me. Not all buds are like this. A few have lovely flowers

As long as you've got some flowers, I wouldn't worry too much. Sometimes, if you look at the outside of the now opened and flowerless bud, you might find a hole has been bored through - there is an insect that does this, usually on clematis, but also on other flowers, and then they can look like this. Otherwise, it's just a genetic coding blip in some of them.

Thanks Bamboo - When is the best time to cut this plant back as it is getting rather over grown?

Unfortunately, its spring when you can cut them back as far as you want, not now. Take off the bare minimum if you're desperate - pruning it too much now will encourage soft new growth which won't have hardened in time for the dreaded W word, winter, meaning the plant will be more vulnerable to dying from the cold.