I think the aircraft IS Liverpool based.
The aircraft coming into AMS from LPL will swap with the aircraft coming in from DSA as will the crew.
So, on a Monday, an LPL crew will fly LPL-AMS-DSA-BCN-DSA. Sleep in Doncaster. Fly DSA-PRG-DSA-AMS-LPL on the Tuesday.
Obviously as the crew will move with the aircraft and this will happen for all the DSA destinations which all fall into similar sectors as the destinations above.