DPs have decided it would be a good idea to have me added to their joint account. Their main concern is that DM has Parkinsons and memory loss and that if something happened to DF she might need help and it would be easier to have me on the account already. I'm OK with this.
However I'm trying to work out how to do this. Their bank (Co-op) has forms to switch between joint and sole accounts but not to add an extra signatory. There is however a "Third party mandate". Is this what is needed?