ETHZ

Good luck,
just simply get over 80% on average in your school leaving exams. I have a friend who has started at ETHZ in September 2016, though she came with a broad-based baccalaureate rather than 'A'-levels. Once you have your results they are very quick at accepting or declining.

You will always need a backup 'plan-B' (somewhere value-for-money in UK, another Swiss uni or perhaps Karlsruhe Institute of Technology etc)

The Swiss national and cantonal administration takes a while to process your documents, for example it is hard to rent a studio in the private sector until you have your documents from the Kreisbüro and it is better to have an actual Swiss address for complete registering at the Kreisbüro. That's a slight Catch-22. You will really need an EHIC (European Health Insurance Card) at a minimum, or you'll need expensive private health insurance.

Many students at Swiss universities book/plan/register-for their accommodation at their university at least 5-6 months in advance. That means finding waiting lists for studios, apartments, shared-flats, finding when that waiting list opens e.g. (randomly choosing as target) May 3rd (it varies from year to year and by organisation) and then try and log online your request JUST AFTER MIDNIGHT ON May 2nd, 00:01am - as many of the waiting lists become full within minutes. You basically have to check several times per week when the waiting-lists will open, sometimes it can be a whole month earlier than you expected! Nice apartments start at 2000 francs per month, without phone, internet or TV. You might be able to find 12m2 student studios for a few hundred quid a month, including wifi, if you book early. You can always cancel your accommodation pre-registration if you eventually choose to go somewhere else.

for visits, or when you are eventually resident, there are many cost-saving options, the half-price student railcard pass (about 180 francs/year) that also gives bike-rental anywhere in Helvetia & priority access to all ski-resorts. Your ETHZ student card will give free bike use around Zürich. Migros/Lidl/Aldi are great supermarkets but meat is expensive, probably best to be vegetarian!

Most lectures at ETHZ are recorded as they are delivered, and are available on an internal YouTube service for browsing e.g. by iPad, which is a very helpful feature for those beginners to German teaching, it's easy to review at leisure the lectures. It is however a very hard working university.