Forgive me if i am wrong but i believe that home to duty rates have decreased. The reasons cited are: 1. Lower petrol costs 2. Lower car servicing costs.
Have a look at
http://www.theaa.com/allaboutcars/ad...trol_table.jsp and
http://www.theaa.com/motoring_advice...s/archive.html - I don't have time to do the analysis.