rescuemycar
Much cheaper than the big names. I've only had to use them once, when I ran my battery down, but they came fairly promptly (I was at a holiday cottage and not in a rush, and told them that, so I don't really recall the response time, just that I don't recall thinking why they hadn't arrived yet).
And the premiums don't seem to change much year on year, unlike those stories of AA/RAC/whoever making huge hikes on renewal and hoping you don't notice.
Maybe response time etc depend on where you are in the country? Especially for the organisations that have local contractors rather than their own staff.