Although I was being spotted by several stations, I was puzzled why I was apparently not spotting others. A quick check the PC showed "no internet access" on the wi-fi symbol: I was receiving many stations but these were not being uploaded to WSPRnet. I turned off the PC and rebooted it . All is now fine again. LA and DK were soon being spotted and uploaded.
UPDATE 2324z: Plenty of MF stations in Western Europe spotted and uploading to WSPRnet. All these are stations I have seen before though. EA5DOM is active although I have not copied him yet. My best DX is DL-SWL (701km) on TX and DH5RAE (995km) on RX. Still using 5mW ERP and earth-electrode "antenna".