physics,maths, chemistry and further mathematics,,,,,although it depends on the university you are applying to..but physics, maths and chem are a definite regardless of the university of choice
Actually most unis only require maths and physics. Some might say "any three from the following list" which will usually include all the sciences and things like maths, further maths, electronics, engineering.
You also need to bear in mind that if the course you are looking at is heavily weighted towards one area of engineering it might require subjects that would otherwise be desired, for example anything in chemical engineering is going to require chemistry.
You need to look at what individual unis want and talk to tutors at the sixth forms/colleges you are looking at. For example Aberdeen want grades BBB including Maths and one other from Physics, Design Tech and Engineering... But Cambridge want A*A*A including Maths AND Physics and ideally one other science, technology or maths subject.