Yes, thanks Luddite. It's difficult to make a judgement based on individual cases but it sounds as if your insurance experience is comparable with a breakdown service.
I've now checked all my policies:
My classics, the Morgan and the Austin 7 are both with ERS and both have breakdown cover. I don't know how much this costs, it appears to be included with the policies. I can't find it as an add-on so therefore I don't seem to have an option of removing it.
My "modern", a Mazda, is with Ageas and
doesn't have breakdown cover. It seems this is offered as an extra for £39.99. However, I notice it is restricted to "roadside repairs" and to cars less than 11 years old. My modern is a 2013 model and I don't intend to replace it any time soon, so it's not a long-term benefit.
My RAC membership for this year was £172. On the face of it, that seems a lot in comparison. However, that gets me roadside and home breakdown cover for any car in which I am unfortunate enough to break down, not necessarily any of the three I own. I have used them more than once under this provision.
I think I shall stick with the RAC but I shall negotiate with ERS at next renewal to see if I can remove their breakdown cover and reduce the cost of the classic policies.