I bought a New pull cable for my battery Isolator at Autosport from Ringspan.
The Cheap one that came with the isolator when routed the way I have routed the cable (a lot of bends) was impossible to pull hard enough to move the isolator.
This new Cable follows the same route and pulls easy....

Simply put these are the best cables I have ever seen for this purpose - They also have some throttle cables...

http://stores.ebay.co.uk/RINGSPANN-U...p2047675.l2563

Click image for larger version. 

Name:	cb62_2.JPG 
Views:	45 
Size:	5.8 KB 
ID:	6738

I will say they are not cheap but worth it if you are having problems with a standard cable..