Ice Dragon by Jeffrey Lord

The provided text introduces Blade, a British agent working for the Dimension X Project, which uses giant computers to transport him to other dimensions. While his journeys aid England, he's also a guinea pig whose physical and mental reactions are extensively monitored. This particular adventure finds him in a dimension plagued by Ice Dragons and their mysterious Ice Master, amidst a conflict between the Treduki and Graduki peoples. Blade becomes involved with the Union, a resistance group, as he uncovers the truth about the Ice Master's alien allies, the Menel, and orchestrates a daring escape and counterattack. The narrative follows his evolving relationships, his quest for understanding the underlying alien threat, and his ultimate mission to expose and combat these interdimensional beings.