A decent aircon certainly does compute in the UK - the good ones can heat as well as cool - so you can use it year round. What's more... the coefficient of power is far higher than any other heating system, since phase-change based cooling doesn't create or destroy heat... it simply moves it in or out.
A typical coefficient of power for an AC unit is about 3:1... so for every 1kW of electricity you give it, you can get 3kW of heat or 3kW of cold. Considering that, it's even more environmentally friendly than the electric heaters they're fitting in most multioccupancy new-builds these days, where new regulations prohibit gas central heating.
Unlike with standard boilers, which can never produce more watts of heat than you give it in energy even if it's 100% efficient (which they aren't)... so if you fit air con instead of a boiler, it's paid for itself in a couple of years.
True... a decent one can cost between about £500 and £1000 to get fitted (if you shop around) depending on whether you fit it yourself or get help from whoever gives the cheapest quote. But like I say... if you use it to heat too, it pays for itself in time, and the modern inverter models can run on as little as 3 amps even on a day like yesterday...
I measure mine with our energy meter and it costs about 8p an hour to run... is anyone seriously telling me they wouldn't pay 8p an hour to be able to sleep without the aforementioned moths, flys, heat etc?
In the past, before I had the aircon... I'm sure I was spending far more than 8p an hour on other methods of keeping cool anyway: like ice creams and cold drinks. Now I can enjoy a hot cuppa too if I choose.
Not to mention the fact that if you suffer from hayfever (as I do)... it's a god send to have no reason to open the windows.
I could go on, but suffice it to say, there are dozens of reasons why AC is useful in the UK, even when it's not hot out.
And for anyone who wants to run high end or overclocked PC's... AC is triply valuable... even if it gets to 38C outside (as it did in about 2006) your rig can still be drawing 14c air across it's chips or rads... I doubt any overclocker could honestly tell me that isn't tempting?
It's a portable one that only comes out during summer, and is then wheeled away for winter. The unit downstairs which is permanent doubles up as a heater, so it's used all year round.