Yes, 3rd party only. While payout performance is a factor where you are hoping to be reimbursed, with 3rd party that becomes Someone Else's Problem, no? While I no longer cover the miles that increases the risk, it is still possible to cause third party damage. For example, the time that my handlebars went and I slapped a parked car up the bum. £12 a year for peace of mind is worth it, £55 for club membership, less so.
Curious that I hadn't come across them before, I assume it is relatively new.