Jagwire do workshop rolls, I've bought cut lengths from a bike workshop. But the distributor who are just up the road from me, Morelarge, won't sell to the public, though you might be able to get a roll via an account holder.
Do you know what the service interval is? I haven't seen any mention of it, I know 4 - 6 years is the recommendation for motorcycle hose, but that's DOT fluid.
I'm used to changing cable housing every couple of years on an all weather bike, and feel the benefit. I'm interested to know if there's a benefit from changing hoses.