Your best and most flexible bet is to stick with what most universities prefer.
No point in taking subjects like CompSc which is not being 'counted' or taken seriously by the Admission when they compare you with other applicants. It would be sort of wasted effort. A grade A in Economics or Physics carries more weight than an A or even A* in Comp Sc. Admissions allocate points to them in an effort to compare different applicants.
Maths, Chemistry and Biology for sure,
and Physics or Economics