Either way, be prepared to be dicked about. Their insurance company’s loss adjuster is there to reduce their costs as much as possible. Your insurance company should fight your case to get you back to a pre-accident situation, but that doesn’t appear to be how it works (in my experience) so you have to fight your own corner.
My advice? Wait for their settlement figure (which will be derisory) and then reject the offer. They’ll get back to you, referring to lots of adverts showing that their offer will buy you a replacement vehicle of the same make and model, maybe in the same colour, possibly of a similar spec, at some address 300-odd miles away. Get a valuation of your car from Glass’ Guide, inform them of this value and tell them you are of a mind to refer the case to the Financial Ombudsman. Make sure you let them know you are aware of section 2 of the Ombudsman’s guidelines on vehicle valuations.
They seem to play on the fact that 90% of people need a replacement vehicle ASAP and so are likely to settle for not quite as much as they ought to. My experience is that the above will get you to an acceptable insurance valuation/payout much quicker than to-ing and fro-ing with adverts and autotrader links.