I seem to be the only one on here with a hybrid by the sounds of it.
Just to clarify, hybrids are exempt from road tax if registered before March 2017, after that it is just the first year only as davew mentioned.
I particularly wanted a diesel hybrid for a variety of reasons but there aren't many that do them. Mercedes do one but it doesn't have a very good reputation if you read the forums, and also Volvo, which mine is. They only did them for a few years and decided that from a marketing point of view it wasn't a good idea. All their hybrids are now petrol. I think maybe Peugeot does a diesel hybrid as well but I wouldn't buy a Peugeot.
As regards pollution, diesels put out less CO2 per mile compared to the equivalent petrol engined car. Nitrous oxides are also taken care of now by the latest generation engines which inject urea solution (adblue). Mine isn't one of these unfortunately.
The biggest problem I see is particulates. The diesel particulate filter should work at low speeds around town but it then dumps the soot when you put your foot down.
Early days yet but I have done about 2,500 miles in my Volvo and I estimate about 1000 of that by battery. Mine is a phev. It plugs in to a 13 amp socket and the 11.4 KWh battery gives a theoretical range of 30 miles. Best I have had is 26 miles though.
With what I am paying for electricity, I am getting 4.2 charges for the equivalent price of a gallon of diesel, so you can look at it as 110 mpg.
I have applied for a smart meter so I can go on a night tariff so hoping to achieve 250 mpg equivalent.
Now I know a bit more about it, the charging points are a mess nationally with lots of different providers. I have found a few supermarkets and other places where it is free but most charge. Some as much as 30p/KWh which is as expensive as diesel or petrol. Having a pure EV car would be nightmare unless you could charge it at home and at work with a fast charger.