Just thought I would update this to say that I spoke to Esure to find out what they would actually value a v6 at should the worst ever happen. They said they would look to pay out between £1000-£2000 (and no that isn't a typo) so those of you who are insured with them and posted here I would suggest you contact them yourselves as you may be in for a nasty surprise.
I decided that based upon this information it was well worth speaking to Admiral again to see what they believe market value for the car would be. They were much better, coming back to me with a price of £10,000. Still not quite the £14,500 I personally believe my car to be worth and a figure I would look to achieve if it were for sale in the current market, but still more than I paid for the car back in 2011.
I will try and get some agreed value policy quotes tomorrow but as the v6 is my only car and I enjoy the fact I get to use it all year round I would expect to cover at least 7500 miles this coming year. Which could, based upon what others have said above make attaining such a policy more difficult, but we shall see.
- William.