Is the insured loss value that they are giving you for the car at an acceptable value to you ?.
If they say 'we will give you 4K' and you rate the vehicle at 5K then you have every right to challenge their complete valuation.
In the ensuing correspondance you can imply that you would probably accept their valuation IF they chuck the car in as well.
It worked for my mate, albeit on a CatD lightly rear-ended Marea HLX, last year.
And dont phone them - written word only. Written words have to be processed and give you a better audit trail.
Just a thought, anyway
(if the car is already at a breakers or authorised garage awaiting confirmation of scrapping you will probably find its not stored in a safe area and bits have been taken off it already - if previous experiance is anything to go by anyway)