RHD 164 throttle cable fitting - how the _____!?

[Jonathan Coates <cdico.demon.co.uk@cdico.demon.co.uk>]

After driving my 164 with a frayed throttle cable which didn't seem to
be getting worse I spent the cash and now have a plastic bag with pretty
logos of snakes and crosses on it. Within the bag is the new cable all
ready to fit once I work out how the thing is changed. Here's what I
found so that someone can tell me how to get the old one out and
(IMPORTANT!!) get the new one in.
Under the bonnet (hood) the cable fixes to the throttle body. No
problem! Then it dissappears under the bulkhead (firewall) where I can't
see where it goes even with a mirror on a stick!
Inside the car there is a metal box which covers the linkages where the
pedal motion is transferred to the wrong side of the car, along with
dummy LHD mechanisms as far as I can tell. I would guess that the LHD
cars look identical as far as fitting this cable is concerned. All the
relevant bits are so far up behind the glovebox, which has never seen a
glove, that I can't imagine getting at the cable without taking off most
of the dashboard (while I'm doing the stepper motor repair?).
In the name of all that is fast, how is this achieved? Is it a really
big job like it looks?
If you can imagine that I'm driving without stamping on the accelerator
then you'll know how badly this needs to be fixed!

-- 
Jonathan Coates
164LV6 Daily driver
752.0TS T car
Alfetta 2.0 GTV Veni Vidi Visa