Main Loom Fitting........

Hello
After cooking portions of my main loom it now has to be replaced (thanks to a poxy short at the fag lighter- bloody smokers!). It is on order from Autosparks including a separate instrument harness. I am planning on plugging it into the chassis loom and engine bay harnesses that currently exist. I don't suspect any problems hooking these up but anticipate the main loom fitting to be a proper headache!
Anyone done this and are there any 'secrets'?

I recently had the main dash stripped apart from that lower dash section with the heater vents/speakers in it. Does this need to come off? It looks like everythings feeds above this so hopefully this can stay in place.

Any tricks to feeding connections through bulkhead grommets/access?

Please tell me no tricks needed and should take all of 15 minutes. I would be in heaven!!

bollocks smorkers are the most interesting fun make life worth ago arent full of i run a mile everyday but dont have any personnality or contribute antything but middle class fashion of the moment idea of any people i know no tricks and should take 4 minuets if you smoke ,probably quite hard for a nervous non smoker