Chances are that you would not get in a uni for engineering unless you did 3 sciences at least. You realize how competitive it is? Humanities and foreign langauges would not be preferred over two other sciences.
Edit: About Oxbridge, it would be a good idea if you looked at the average tariff points. It's around 570, which is 4 A stars, but in decent subjects.
Possibly, it's been a while since I went through this. The key two subjects are obviously Maths and Physics, with Physics being the also ran. Chemistry is sort of okay, but it suffers from not being Physics. Biology is slightly more scientific than Geography, it's honestly a waste of time to study.
I hated History as a kid, and knew nothing about it - which is a shame, as it's probably the most important Humanity subject to have in a formal and balanced education - and as i've got older see the value of it - and have come to appreciate it much more.
If I was doing this all over again, i'd go for (in this specific order)
Mathematics
More Mathematics
Physics
History
German/Chinese
It is all well and good going pure numbers/science - but some level of Humanities help to balance you and give some perspective.