Ok, time for some explanations.
To answer Alan (mearcats) question the heater/demister unit stiil draws air from the drivers side penetration that goes from underneath the dash to the inside of the drivers side wheel-well. And thats as far as it goes. I will have a membrane over mine so that air can enter and water cant, and a length of flexible hose to the heater unit.
I kept my heater for exactly the reason MM stated - its a requirement by law. Seeing that I have a lot more work to give my Engineer, I wont do anything to endanger our excellent relationship and him have any cause to second-guess anything I do. This is a problem we have with Barbie, as Tony doesnt want to keep his heater/demister unit, but he wont get it certified without it - we are trying to work around this so everyone is happy.
Josh - my cables exit the firewall to the right (drivers side) of centre and dont seem to foul the heater/demister unit at all. Mind you, when they are attached there is no slack. I originally bought them out through the centre-line, but found there was a bit of slack in the cables (just like Deans, he got his shortened I believe), and the angle gave the cables a bit of extra resistance and the shift was very stiff. By shifting the penetration to the right of centre, even though the angle is slightly more than 90 degrees, the lack of slack cable makes the shift not so bad (as the slack made the cables 'snake' when I tried to affix them to the floor).
I hope that explains the setup on The Cat - please say if it needs further explanation.
Pic of where the penetration goes through the firewall:
Cheers,
Tricky