Thanks mate, your explanation is correct. Its not a company car though so BIK wouldn't apply to me but the OLEV grant obviously does.
I've driven a top of the range Prius for the last 4 years merely because of the fuel economy. The car reads 133K on the clock now yet it delivers 65mpg! I'm not a slow driver and most of my driving are on motorways but I can get only 7 mpg below what Toyota claims for a brand new Prius (72mpg)- even for a 5 years old car. It's all down to driving style (skill) as everyone knows. However I am concerned that the figures spoken here are way below what Mercedes claims (134 mpg)! As a senior engineer, I am well aware of the electronics and mechanical facts of a Plug-in Hybrid but I find it difficult to comprehend the large gap. A modern 2.0 liter Petrol engine should be able to deliver at least 55mpg on a reasonable torque and BHP. I just assume that by considering the weight to power ratio and the extra drag of an electric motor trying to charge a 6KW depleted battery pack, one might be able to justify the 40-45 mpg figure. But then that defeats the purpose of a PHEV.
I guess that we have to wait for more input into this issue before making a judgment.