Dryness at the roots can cause this, and I have to say the compost in that pot doesn't look particularly damp, although that may not be the case at all, I don't know. Try giving it a good drink by standing it in a tray, watering it till it runs out the bottom, leave it for 30 minutes to an hour, then empty out the tray and let the pot drain down. If that doesn't do the trick within a day, spray the flowers and stems with water - but not while its in sunlight.

Have you checked it for white mites? I would check for that as well.

My money is on it being dry, try the watering as Bamboo says.

Cold nights will slow the opening process, too, Steve. Otherwise, it looks pretty healthy, to me! If the flower buds are turning yellow and dropping off before they open, that may be too much water, or irregular watering.

Hi
The watering is fine the garden gets watered every evening when we have had no rain Tug you have a good point about the nights being cool so it will get moved into the greenhouse for a short while at night thanks for all your help
Steve

I think you may regret that in June Steve? Tug lives in Arizona and the nights there are quite different to ours.

When I say cold nights, I mean temps less than 10º C.

Deffo the cool nights - mine is blooming prodigiously in the conservatory. As much light as you can give it, and as stated, regular misting is appreciated.