Barry P,
you only have a 60 litre tank.
1. Go to B & Q, get a 10 litre bucket for 98 pence.
2. Go home and empty 10 litres of tank water out of your tank into the bucket.
3. Empty the bucket and rinse.
4. Fill the kettle from the cold tap and boil it.
5. Once boiled tip the whole lot into the 10 litre bucket.
6. Stick it under the cold tap and start filling. As you do so add your dechlorinator.
7. Once up to 10 litres turn off the tap.
8. Your bucket of water will now be of a temperature anywhere around 24 - 28 degrees. This will
not place your fish in any danger whatsoever.
9. Pour the water into your tank.
10. Job done in 5 minutes. Almost a 20% water change done with one bucket of water

.
steve