Many people go to the UK in summer to study English. Typically, they enrol in a language school for a fortnight (=two weeks) or even longer, and attend language classes in the morning. In the afternoon, there is often a choice between supplementary (= extra) lessons, or social activities, such as trips to museums or places of local interest, or sport activities. The school will probably also book your accommodation.
Maybe you will stay with a local family on a full-board (= accommodation and all meals included) or half-board (= accommodation plus breakfast and dinner) basis, or perhaps you will stay in student accommodation, such as a hall of residence (= specially-built accommodation for students attending English universities).
Before you start your English course, you'll probably need to do a placement test, which will assess your language level. If you're attending a business English course, you'll probably also do a needs analysis, which pinpoints the areas of business English that you need to work on.
Most language schools offer a range of courses. For instance, you might decide to have your lessons in a small group, or you might prefer a one-to-one or individual course. Schools also offer exam-preparation courses (for the Cambridge or TOEFL exams) as well as YL (young learner = children) courses and ESP (English for Specific Purposes) courses.
Your teacher should be TEFL-qualified, which means that he or she has undergone specific training to teach English as a foreign language. He or she should be sensitive to your problems or needs, as well as able to manage the classroom effectively and to provide a range of learning activities.
However, it's also true to say that you "get out what you put in": the harder you study, and the more you take advantage of being in an English-speaking country, the faster you will improve your English.
More tips for learning English abroad
Practise as much as you can outside the school. Being in an English-speaking country gives you a great opportunity to try out your English. Don't just say "hello" or "goodbye" in shops, for example. Ask questions or ask for advice to get someone else to talk to you!
Learn about the culture as well. If you're staying with a host family, you have a chance to find out more about the traditions in their family, or community. Ask them about their likes and dislikes, hobbies or interests, or what they do on special occasions such as birthdays, or at New Year. You'll learn new vocabulary as well as other interesting information, and of course, you'll get another good opportunity to practise your speaking and listening skills.
Talk to other non-native English speaking people! Places like the UK attract lots of foreign visitors, giving you the chance to understand a much greater variety of accents and ways of speaking English. As English is spoken globally, it's important not to limit yourself to only trying to understand native English speakers.
Try out the bookshops. Although online book shopping is easy and convenient, going into a bookshop is a fantastic experience. The bigger shops in cities like London stock a huge range of English learning books, and you can browse other sections for books on your personal interests.