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.
Find all the alternate title screen skins.
Clean 1000000 things.
Save the Man in Black.
Die 1000 times.
Win The One Tournament.
Defeat the helicopter boss.
Travel to the secret moon base.
Defeat the Ether boss.
Defeat the Fire boss.
Catch 200 objects.
Defeat the Air boss.
Watch a train arrive and leave at any station.
Defeat the Water boss.
Buy all possible shop items..
Find an alternate title screen skin.
Find a secret room in the mansion.
Defeat the Earth boss.
Reunite with Heather and the Old Lady.
Go on a most excellent adventure with the Professor.
Meet up with Alice and Sim.
Kidnap Mr Deck from the TV Studio.
Get the high score on all the arcade games.
Take your first train ride.
Earn £10000 from jobs, junk yards and other winnings.
Help to make bricks.
Help to sort the post.
Buy an item from a shop.
Play an arcade game.
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.
Return the blind man's cat.
Clean 10000 things.
Of dead Old Men?
Rescue the family from the burning house.
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.
Don't save the Man in Black.
Complete the game.
Clean 100000 things.
Earn £1000 from jobs, junk yards and other winnings.
Find all the secret rooms in the mansion.
Score 100 baskets in total.
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...