The weather in the uk has been very unseasonal with so much rain and not enough sun. Hopefully it will warm up and all the flowers we are waiting for, will bloom.

You haven't said what you did next, after planting the tubers in baskets - if you put the baskets straight outdoors, that would easily explain the late flowering, its more usual to start them off indoors, in pots, then transfer to your baskets when the weather starts to warm up ready to go out when we get to the end of May beginning of June, after hardening off. Either that or plant straight into baskets but keep the baskets in the greenhouse or somewhere till end of May.