Assuming I have understood you, I think these got a recommendation
https://www.ebay.co.uk/itm/DELPHI-Suspension-Arm-Track-Control-Arm-for-ROVER-75-TC1261-Mister-Auto/191695637167
https://www.ebay.co.uk/itm/DELPHI-Suspension-Arm-Track-Control-Arm-for-ROVER-75-TC1260-Mister-Auto/311448485765
I don't think the ball joint is separate.
There is mention on the forum, that these can be changed by just lowering the sub frame slightly. I am not sure if the bolts for the rubber bushes could be torqued up due to lack of space
macafee2