ANTS

Welcome to the site Matt 

Ants will loosen the soil but generally do not do a lot of harm.  Some people report they eat roots but I've not experienced it myself.

There's some information about clearing a plot here, if you need it
http://www.allotment-garden.org/articles/Clearing_a_New_Allotment.php

Bindweed and maretail are both nightmares, you're right 

Regular attention is the best way to keep on top of them once you've reached that stage.  Good luck!

Ants are a nuisance in our garden - we have a colony of rancher ants - they herd aphids onto our herbaceous plants and vegetables and milk them for some sort of sugary substance which makes the plants horribly sticky.  We have a friendly woodpecker who tries to keep them under control but often have to resort to ant powder or boiling water.  

PS - after writing this post, I thought I would google ants+aphids and came up with this link: http://science.jrank.org/pages/462/Aphids-Ants-aphids.html