For the benefit of others, the uninstall / install details are as follows..
Uninstall Bnd Tools v7.1.x
Eclipse | Help | About Eclipse IDE | Installation Details | Installed Software | Filter on ‘bnd’ | One-by-one select each Bnd Tools entry | Uninstall (ignore the restart prompt until the last entry) | Restart Eclipse
Remove Bnd Tools v7.1.x from available update sites
Eclipse | Help | Install New Software | Manage.. | Select entry for Bnd Tools v7.0.0 | Remove
Install Bnd Tools v7.0.0
Eclipse | Help | Install New Software | Add.. | Name=OH Bnd Tools v7.0.0 Location=https://bndtools.org/bndtools.p2.repo/7.0.0/ | Accept certificates