Buy a plastic dustbin or water butt (less than a tenner), they'll hold around 80 litres. Place as much water in it from your tank as you can while still being able to lift it along with your fish, heater and pump (or filter media if you have an external. You may have to bag it up if it's loose). You could put the rest of the water in buckets or loose it and top it back up once moved. You'll now be free to clear the tank and move it!