As it was reported on other websites. Impellor thread had stripped allowing slippage on the shaft.
Pump housing is plastic welded together so it will have to be replaced as an assembly.
Disassembly was achieved by removing top and sides then turning upside down and removing heaps of screws until the bottom came off. Pump just pulls out of the rubber seals from the suction and discharge connections.
Now to wait for new pump.