I'm with the RAC because I get a good deal with them through my insurer. On the few occasions I've called them out they've been there in under half an hour.
The RAC and the AA are the only breakdown services with their own staff out on the road. Other services use local garages to come to your aid; they might not be as good at providing
roadside repairs as the AA and RAC are, as they can sometimes be in rather a rush to get your car onto their low-loader to take you home or to your destination.
However I've used Autonational Rescue in the past (who are among the cheapest providers) and I was generally very pleased with the service that they provided:
https://www.autonational.co.uk/