Do you have any figures about this? Mobile air conditioners with COP of 2 or so are being developed these days (IPCC/TEAP special report, page 306), and I can't imagine the energy consumption is significant compared to the actual transport, unless the temperature differences are extreme. I'm willing to be proven wrong, though.
There's some information about visiting students in Cambridge.
Very few students are accepted, especially in technical subjects, and they normally study the first or second year (so compsci part IA or IB, not II). Cambridge also has an established exchange program with MIT, where applications are somewhat less competitive for those coming to Cambridge.