In reply to Anti-faff:
Just check on the Glacier Line, not sure if its the same animal as a normal double, for instance, this warning would suggest otherwise:
----Glacier half rope with SuperDry finish. Only available in 30 and 40 m lengths.
----*Under no circumstances is this to be used as a single rope for mountaineering or rockclimbing.
I linked to a Dicks Climbing special the other day, a 9.8mm single that you can buy in a 30M length, it was dry treated too for £55