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.
Read 15 teletext pages.
Find all the secret rooms in the mansion.
Complete the auto map by visiting every room in the mansion.
Get the high score on all the arcade games.
Complete the game.
Reach the end of the game having cleaned one million things.
Clean 1000000 things.
Find all the alternate title screen skins.
Save the Man in Black.
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.
Defeat the Water boss.
Buy all possible shop items..
Die 1000 times.
Push all the rubber ducks into the water in the Laundry Room.
Catch 200 objects.
Find an alternate title screen skin.
Find a secret room in the mansion.
Defeat the Air boss.
Defeat the Earth boss.
Watch a train arrive and leave at any station.
Get the kids blamed for shop lifting.
Reunite with Heather and the Old Lady.
Kidnap Mr Deck from the TV Studio.
Run the BASIC program everybody knows and loves...
Meet up with Alice and Sim.
Earn £10000 from jobs, junk yards and other winnings.
Go on a most excellent adventure with the Professor.
Clean 100000 things.
Play an arcade game.
Take your first train ride.
Help to sort the post.
Help to make bricks.
Buy an item from a shop.
Earn £1000 from jobs, junk yards and other winnings.
Earn £100 from jobs, junk yards and other winnings.
Help to wash dishes.
Empty 10 bins.
Spring Logan from prison.
Learn to play the drums.
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.