My broad beans are still in the seed packet, Keith. Is it because you live in the south and have had an unusualy cold, wet winter which has killed the beans?

Sounds like they are over-wintered crops that have had too much water, or have been sown in autumn on wet soil. If this is the case then you have a fungal disease. For future growth you will need to introduce better drainage, increase the potash fertilizer and maybe even lime your soil to kill the fungus. Personally, I would replant broad beans in a different, free draining area.