Gas instalations are VERY popular in Poland - installing good one in reputable garage costs around 800 pounds. There is no known issues with those instalations, running is cheap as chips.
Problem in England is, that people usually changing cars here every 2-3 years, so if car is not company car or taxi, investment will HARDLY return. Also lack of gas pumps on gas stations can be a problem. Other than that (and bullshit about danger of explosion in garages or ferries) I have no idea, why is this so unpopular here.
There is also few projects to convert cars to gas we using in our cookers and central heating. I belive in works already in US, there is few companies there renting mobile gas pumps you can connect at your house and tank your car