You asked about organic weedkiller in chat the other night. Well there isn't really a totally organic chemical way of getting rid of weeds but this is the one that I was thinking about, its based on Ammonium Sulphamate, trade names seem to be Amcide and Deep Root. The links below may help.
www.growingsuccess.org.uk/detail.asp?PR ... eed+Killer
You would have to explain to your client that it isn't a totally organic solution but if time is short may be the most practical.
If that is not acceptable then think you are back to digging the weeds out by hand or if they are not in a rush dealing with the weeds by covering them with light excluding fabrics for a year!
Hope some of the above is a help
Deep Root seems to be the one , Its bloody strong for "near" organic !! A goodun
Im sure I will be able to persuade them that this is a clean alternative, thanks again