When I renew my car insurance, my insurer tries to sell me breakdown recovery from the recovery organisation they are associated with. Is this OK or should I buy it separately?

Car insurance companies frequently negotiate bulk reduced rates for breakdown cover with recovery services. These rates should be cheaper than the standard rates the recovery services would offer you direct. So I suggest that you get some online quotes and compare them with the rate your car insurer has offered. Then check out what each policy covers, and accept the cheapest which gives you the cover you need.