Cleaned the car and after drying the black was still dirty, more stained. Looks ok when stood up, but down close a bit stained and lumpy. A quick Google and someone suggested Zymol on the XF (I think) forum
I find this very good on all black areas - https://www.ebay.co.uk/itm/Autobright-Car-Wax-Polish-Sealant-Zonyl-PTFE-Paint-Sealant-with-Carnauba-Wax/330904430680?epid=1963629819&hash=item4d0b70e858:gqIAAOSwYSlXhNHb