>>> even the blue badgers have to pay
You've got blue badgers in your part of the country? They're black and white everywhere else!
;-)
(On a serious note though, if you're a regular user of the hospital car park, it might be asking if there are any discount schemes available. For example, as an oncology patient at Ipswich Hospital, I pay just £3 to cover a total of 10 parking sessions, with no limit on how long I stay for on each occasion).
I didn't pass my driving test until I was 37 because, up until then, I'd been living in Sheffield, where there were 17 buses per hour passing near to my house all day and all evening, with a skeleton service of buses running through the small hours of the night too. I found it far cheaper to use public transport (including taking occasional taxis when, say, I had to get to an urgent meeting) than to consider learning to drive and buying a car.
Then I moved to Suffolk, where a car became far more useful due to there being less public transport available. So that's when I starting taking driving lessons. I later had a few years of being largely unemployed though, and couldn't afford to run a car, so I've experienced life without one here too.
For me, while a car isn't totally 'essential', it certainly makes life a lot easier. For example, it costs me about £3.50 in fuel to drive to the hospital and back, whereas it would cost £70 by taxi. (Even the charity-run transport service, which tries to help cut the costs of getting to and from hospital, charges over £40 for the return trip. As I'm currently attending the radiotherapy department on 37 consecutive weekdays, there's no way that I could afford such prices!). I can get there and back by taking two buses (or a train and a bus) but it adds considerably to the time taken out of my day just to attend a 15-minute appointment!
So I'm not rushing to get rid of my car but I can understand why you might be considering it if the taxi costs that you'd be facing were significantly less than what I'd have to pay. (It's also worth thinking about things like shopping. Some people are happy to order everything online but I still prefer to browse around the supermarket aisles, so a car is useful to me in that respect).
However we can't really advise you with regard to a 'mileage cut-off point' without knowing how near or far you are from the places you need to get to and how often you'd need to get there. Only you've got that information available to you, so it's only you who can do the sums.