Most of what has been said has been covered but speaking as someone doing a Civil Engineering degree (having sometimes thought what it would have been like doing Mechanical Engineering instead), the only person who can decide which course is yourself. As you have just started your A levels, you have still got plenty of time to decide, so you should spend time deciding which course you want to do, rather than rushing into it.
As for entry grades, you are best looking at the websites of the universities you are interested in. For a master's degree (in Civil Engineering) my offers were generally 2 As and B. Some also specified an A in Maths, so i would consider this the most important course to take. Physics is also very useful, as is taking Mechanics as an option in Maths.
As for media, you're probably better doing something thats more related to engineering.