I tested the game and unfortunately the internal battery in the cartridge has gone dead, which means the game doesn't keep your save when you turn off your device between playing sessions. Apparently the battery can be replaced, but I don't want to mess with the cartridge without experience in soldering.
This game has been living in my storage for over 15 years now, but I hope someone else gets more joy out of it in their collection.
Will be shipped within UK with Royal Mail Special Delivery or Tracked for international delivery.