Pictures will help.
As a guide, the first time my 2004 ex Police 3.2 was written off, it was valued at £2,000 (2009 with 120k), and the last time, £1,500 (2013 with 250 ish k).
I sold it in reasonable condition for the (270+k miles) as a fully functional Police car (minus the livery) for £1,400 iirc... The lightbar alone was £750+ which gives you an idea of what an ex Police car is worth.
Another ex Police Omega with full service history was around £1,700 and full history and 153k. I sold that in 2012/3. The full history from TVP for that car included an invoice in 2003 for the purchase of the car from VX... £18,300 and also receipts for over £12,000 in body repairs at VX from two separate collisions and another £4-5k bill for a new engine caused by driver error.
All fairly typical for a Police car, and your insurance knows it. Incidentally, both of those cars went to NI. One was fully restored in an old PSNI livery, tother was later sold to a chap in Eire.