I have found in the past most travel insurances cover you for the Camino. I have one though my bank account and the only time they ever questioned me was for Camino Frances because of the height in the Pyrenees. Apparently above a certain altitude they consider it mountaineering not hiking but they were ok with it. I don't think you will find a problem with the Ingles. I am also aiming to start Ingles on 27th September maybe we will bump into each other.
Regular travel insurance is sufficient for Spain. Just a matter of what level of cover you want.
Remember that you should also have your EHIC (if still in date up to your expected end of Camino) or the new GHIC. Some insurers will require you to have one.