I've gone as far to offer the mother of a neighbor in England to drive her about 100+ miles to Gatwick Airport. She offered to pay me the amount she would've had to pay a taxi, but I said, "Nah, it'll be an adventure". But driving through central London, across the Tower Bridge and on to Gatwick Airport, and back, was such a pain in the buttocks that I took the money. (Being a poor junior enlisted guy was another factor.)
One of the smarter things I ever did was not rent a car in London.