12.1 Ice Heist! by Guy Adams
Recently, the world changed for Margaret Hopwood. Everything she knew was turned upside down by the arrival of a strange man in a blue box. And now nothing in her life seems the same. So when he comes back with a lady called Leela and an invitation to an unusual art gallery, she's more than happy to join him for the ride. And what a ride it is. Because it’s an art gallery on a distant world… where a deadly plan is about to commence - one involving creatures called Ice Warriors.
Note: This title is also available on CD as part of Doctor Who: The Fourth Doctor Adventures Series 12 Volume 1