Jet Set Willy II: The Final Frontier was a platform game released in 1985 by Software Projects for a variety of 8-bit home computers. It was the only official sequel to Jet Set Willy, one of the most successful and popular home computer games ever released. Officially, Jet Set Willy II: The Final Frontier is the last of the Miner Willy series, although numerous unofficial sequels, remakes, homages and updates have been released, even up to this day.
Jet Set Willy II is an expansion of the original JSW rather than a new game unto itself. Its map is primarily an expanded version of the original mansion, with only a few new original elements over its predecessor, several of which are based on rumored events in JSW that were in fact never programmed (such as being able to launch the titular ship in the screen called "The Yacht" and explore an island). In the ZX Spectrum and Amstrad versions Willy is blasted from the Rocket Room into space, for which 33 rooms he dons a spacesuit.
Source: Wikipedia, "http://en.wikipedia.org/wiki/Jet_Set_Willy_II," available under the CC-BY-SA License.
Individual credits:
Derrick Rowson: program