There's no easy way through on the passenger's side. What we tend to do is drill a hole through the bulkhead and grommet it between the brake master cylinder and the inner wing. The only really easy way through is on the driver's side - remove the radiator expansion tank (1x10mm bolt) and there's a huge grommet with loads of spare cable tubes on it.

Dominic

Cambridge Car Audio
http://www.cambscaraudio.co.uk