some of mine are just making buds whilst others have been flowering for weeks. so just give them more time.

thanks

Watering with suitably diluted tomato feed might kick start them.

mine from seed just started to flower they are a late flowerer but watch out for earwigs attacking the petals when in flower.Iagree with the tomato feed.comment.

I have used tomato feed but am not sure of the amount or how often to use it.

Make it up according to the instructions, as for tomatoes and water it on from time to time. Approximately weekly from midsummer til they're flowering adequately seems to work for me.

Thanks to everyone who replied