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 2008 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)
Two of the Slitheen-Blathereen used a similar,less complex ship as a base in Antarctica during their plan to spread Rakweed across the Earth,this ship had a dining room were they ate Rakweed,the ship was left abandoned after the Blathereen were killed, it is unknown what happened to it afterwards but is possible it was found by UNIT. (SJA: The Gift)
In their plan to turn Justicia into a planet destroyer, the Blathereen used a huge Mothership, however it was destroyed by a solar flare. (NSA: The Monsters Inside)