[kadriah]

I am getting small insects that look like small greenfly, gathering in large numbers around the base and root of my herb plants,, they seem to be eating the roots. also when I water my plants they all float to the top but dont drown.
I've had this problem inside a few years ago and the only non harmfull way i could think of getting rid of them was to wash the roots of the plant and plant it in new soil, but this seems an impossible task outside 

could any one give me any advice or recommend something to deal with them?

many thanks

[Hey Jude]

Have you tried soapy water spray? - it seems to clear a lot of unwanted things in my garden. Jude.

[kadriah]

i will give that a try, thanks 

[Spana]

They sound like root aphids.  Give the soapy water a try or squirt them off with a fierce hose pipe. keep doing it until they give up

[kadriah]

i've given the soapy water a try but its a bit hard to see now as its gotten dark out,
many thanks again for the tips, i will keep you up-dated 

[Arbutus]

Be careful to use vegetable based soaps (like Ecover etc) only as others can damage the plants, and those with antibacterial properties will destroy all of the beneficial soil microbes too.

There are a variety of "home brew" remedies you can try on aphids and many other sap-suckers and leaf-munchers too.

There's an interesting article/list on Ecocharlie which highlights a few options:

 http://www.ecocharlie.co.uk/blog/index.php/2010/03/08/plant-pests-%E2%80%93-ten-top-organic-solutions

I particularly like the idea of using the natural defences of one plant (be it garlic, chilli, rhubarb) to help guard another, and of course you don't have any potentially hazardous chemicals on your herbs.