The Slitheen craft was a spacecraft used by the Slitheen. It has faster-than-light travel capability in the form of a slipstream engine.
It was the ship that crashed into Big Ben and the River Thames in 2006, the Slitheen using the crash as a diversion for their bigger plans, namely, their attempt to destroy Earth.
A bigger ship waited in orbit above the North Sea and was probably similar in design to the Slitheen craft. (DW: Aliens of London)
There was another ship near Earth in 2009 while the Slitheen stole the Earth's power. (SJA: Revenge of the Slitheen)
It was later seen leaving Earth after the moon almost collided with Earth. (SJA: The Lost Boy)