I love the way you Poms (that's a term of affection from we Aussies) think waking up to 22 degrees is warm. Here in Melbourne, Australia, summer temperatures reach 45 celcius and we can have a week or more at a stretch where it's 40+ every day and in the high 20s overnight. By the third or fourth day of it, even the air-con is struggling to keep room temperatures below 30. So without a chiller, it's all hands to the ice bottles I'm afraid. Plus lots of fans and extra partial water changes.
PS We also get pretty cold in winter - it's 4 degrees outside currently (at 6.20am) and can go down below 1 degree.