Hugh Chaloner wrote:
Hi,

I'm being plagued by a particular growth on my beds here in Dublin,
particularly in the rocket and cress. I'm at a loss to identify it. Is
there an online directory of weeds anywhere and suggestions how to
eradicate them?

This site is good to find what you've got:

http://theseedsite.co.uk/seedlings11.html

Hoe and dig regularly. I don't use chemicals.