There are a variety of organisations and universities that provide subject-specific vocational courses during the school holidays for those considering A level choices or university.
Science, Technology, Engineering and Maths (STEM) vocational courses
Cyberfirst - Cybersecurity residential and non-residential courses. Free/heavily discounted. In addition to day-time challenges and study, Cyberfirst residential courses often provide evening social activities, so they can be a good opportunity to meet like-minded students. 2019 courses will be listed here , as well as on the Smallpeice Trust website (see below), as soon as they are available. Places on free residential courses fill quickly. Applicants for courses usually have to complete a timed (but not too stressful) online maths test and also complete an online personality profiling quiz, before being accepted. Cyberfirst also organise several non-residential taster days for younger teens during the year. See their website for updated information.
Headstart STEM residential courses, including product design, forensic science, robotics and the Inspire girls-only course for engineering, science, maths etc. Aimed at Yr11 and 12, ie approx age 16-17. Bursary support for some courses to families in financial difficulties.
Smallpeice Trust - STEM residential and non-residential courses, mostly for Yr10 and above, held at various universities, nationwide. Courses tend to be subsidised; those designed to attract particular groups of students (eg. engineering for girls) are often very heavily discounted. Popular (and cheap) courses can fill quickly, so apply promptly. Join their mailing list and follow their Facebook page for notifications of new courses.
University of Kent - Space school - Astronomy weekends for 11-18 year-olds - several in August and some at other times.
University of Leicester - Space school Residential courses for ages 13-15 and 16-18