Petra, I read your thread earlier this morning and waited to reply after giving it considerable thought whilst making the bed, tidying up etc.etc. wondering what I would do under the same circumstances.
I also have several friends, although quite young, have also given up their cars and do not regret it at all.
The computer and internet win hands down for me. Some great internet deals are out there. I can watch TV and film and listen to the radio though the computer, order my shopping, skype for free with the grandchildren, make very cheap phone calls abroad with skype, research everything I want to discover every day and communicate with friends. I also have all my photo collection stored there and e.books etc.etc.
The car does not compete, unless you do live in a very remote area.....then I would "run the car into the ground" if you can still afford the car insurance, tax and petrol for the time being. In the meantime, as other Gransnet contributors suggest....look into every possible means of increasing your pension through benefits and tax etc.etc.
If you do live in a remote area, could you seek a reciprocal arrangement with neighbours...think I read about this somewhere in the UK where retired neighbours help each other with the shopping trips, hospital visits etc.etc. Then you could use a bartering system and do something for a neighbour that they would otherwise not be able to do (e.g. gardening, cooking,?? etc.etc.) I give my neighbour a weekly massage (I am a qualified masseur!!!) in return for favours she does for me.
Also, if you want to go somewhere for a few days and can afford the fee, you can get some very cheap car hire in some areas. When I looked after my Mum following a hip operation (she lives 2 hours away from me)....my husband needed his car back home, so I stayed with Mum and hired a car for a week in her area (SE England) so that I could take her for hospital visits etc.etc. It cost me £110 for seven days.....and the petrol was minimal as it did 70 miles to the gallon.
So good luck with your thoughts. Hope the above helps a little.