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