Don't you need to have a trade account to use English Braids? I was looking at their site last week and couldn't work out how you would order from them unless you set up an account.
The problem is that you want olive. If you wanted something with a bit more visibility it would be easier. I was looking at this stuff:
http://www.cleats.co.uk/home/details.asp?id=12
Also looking at the performance dingy lines at
www.ropeloft.co.uk
The Outdoor Shop in Stoney Stratford lists Beal 2mm Accessory cord, but I am a little leary of buying accessory cord without knowing what type of fibre they have used. I bought some Roca cord from The Complete Outdoors (currently they too have 2mm) but it seemed to have a lot of stretch. I think some cord is nylon and some is polyester with the polyester having less stretch, which is what I want. With the sailing folks, stretch is important and they aim to minimise it.
I have some Dynema 1.8mm line from Pointnorth, but have yet to fit it to anything, so don't know how it works. I have read that the polyester sheath on such cords can be prone to slipage on the smooth Dynema core, but whether that is only an issue for climbers, or if it might happen on guy lines is something I will have to find out.
Best of luck