Here is the full list of all 58 Horace achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Travel to the secret moon base.
Defeat the Ether boss.
Complete the auto map by visiting every room in the mansion.
Clean 1000000 things.
Find all the secret rooms in the mansion.
Die 1000 times.
Defeat the Fire boss.
Find all the alternate title screen skins.
Push all the rubber ducks into the water in the Laundry Room.
Run the BASIC program everybody knows and loves...
Defeat the Air boss.
Find a secret room in the mansion.
Catch 200 objects.
Defeat the Water boss.
Buy all possible shop items..
Defeat the Earth boss.
Watch a train arrive and leave at any station.
Find an alternate title screen skin.
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.
Clean 100000 things.
Play an arcade game.
Take your first train ride.
Help to sort the post.
Earn £10000 from jobs, junk yards and other winnings.
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.
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 all other achievements.
Win The One Tournament.
Defeat the helicopter boss.
Save the Man in Black.
Don't save the Man in Black.
Complete the game.
Reach the end of the game having cleaned one million things.
Get the high score on all the arcade games.
Score 100 baskets in total.
Read 15 teletext pages.
Get the kids blamed for shop lifting.