Here is the full list of all 58 Horace achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Reach the end of the game having cleaned one million things.
Save the Man in Black.
Don't save the Man in Black.
Win The One Tournament.
Defeat the helicopter boss.
Clean 1000000 things.
Die 1000 times.
Travel to the secret moon base.
Defeat the Ether boss.
Find all the alternate title screen skins.
Defeat the Water boss.
Defeat the Fire boss.
Find an alternate title screen skin.
Defeat the Earth boss.
Find a secret room in the mansion.
Buy all possible shop items..
Defeat the Air boss.
Reunite with Heather and the Old Lady.
Go on a most excellent adventure with the Professor.
Meet up with Alice and Sim.
Earn £10000 from jobs, junk yards and other winnings.
Kidnap Mr Deck from the TV Studio.
Take your first train ride.
Help to sort the post.
Help to make bricks.
Buy an item from a shop.
Play an arcade game.
Earn £1000 from jobs, junk yards and other winnings.
Earn £100 from jobs, junk yards and other winnings.
Help to wash dishes.
Complete all other achievements.
Spring Logan from prison.
Learn to play the drums.
Defeat the Nanobot Boss.
Empty 10 bins.
Defeat the K-Bot 100 Boss.
Use the Atlas Gloves to tidy up the village hall.
Of dead Old Men?
Rescue the family from the burning house.
Return the blind man's cat.
Clean 10000 things.
Venture out of the mansion.
Climb walls with the Shoees for the first time.
Clean 1000 things.
Clean up your first thing.
Completed basic robot training.
Complete the game.
Clean 100000 things.
Watch a train arrive and leave at any station.
Find all the secret rooms in the mansion.
Get the high score on all the arcade games.
Score 100 baskets in total.
Catch 200 objects.
Read 15 teletext pages.
Get the kids blamed for shop lifting.
Push all the rubber ducks into the water in the Laundry Room.
Complete the auto map by visiting every room in the mansion.
Run the BASIC program everybody knows and loves...