Taxis should be taken only if it is really necessary, because although plentiful, they are quite expensive. Rates differ according to the time of day with the most expensive fares being charged late at night. Mini cabs, of which there are several companies, can be hired through free apps.
Driving in central London is possible if you rent a car or have access to a vehicle, although it is not suggested, as London can be tricky and complicated to navigate, especially for travellers.