How many subjects can you pick? (I am not 100% familiar with the UK education system)
Maths is good, likewise English, Science is good too.
Languages are bloody useful on the continent and you're hassling for fuel. French is extremely useful at Paris Charles de Gaulle so you have an idea what's going on around you.
However, pick the subjects that you enjoy and you are likely to get good grades in.
*re languages, go for french over german. The Germans speak very good english so it's not a problem. I rarely hear german spoken on the radio, french, another story.