In order to avoid the rear driveshafts, i need to route my handbrake cables round a chassis member. What would be the best way to support it? I do have a section of the outer casing from the donor car. Would it be ok to just split this, put it round the cable where it runs near the chassis and p clip it to the chassis?

I put it though some P CLips of the right size. You can get "rubber lined ones"