Rough details
Full details of the statutory charges can be found in the Road Traffic Act (Retention and Disposal of Seized Vehicles) Regulations 2005 - Amended 2008. This document is available on the internet.
These charges vary according to the weight and condition of the vehicle. In most cases these charges will be:
Motorcycles - £150 removal charges and £10 per day storage charge
Car and light vans - £150 removal charge and £20 per day storage
Disclaiming a vehicle
If you do want to reclaim your vehicle from the pound, you should attend with proof of identity and ownership and sign a disclaimer. For vehicles seized under these powers there are no charges to pay if the vehicle is left at the pound for disposal.
Source
http://content.met.police.uk/Article/Reclaiming-a-Seized-Vehicle/1400028464360/1400028464360