In many parts of the UK (including my own), IB is simply not an option in the state sector. However, with careful selection, it is perfectly possible to retain breadth at A level.
Psychology A level links to the physical sciences, has a statistical element and an essay element.
Maths A level has algorithmic and statistical aspects that feed into computer science (whether or not the latter is studied at A level).
If Maths A level is not on the cards (whether motivation or aptitude), then some settings offer Core Maths alongside A levels.
As mentioned above, an EPQ could be taken to extend the range. Also bear on mind that Geog, History and Eng Lit include an NEA (coursework) component, depending on exam board.
So Maths, Chemistry and Psychology plus EPQ or Maths, Chemistry and a humanity plus EPQ or Chemistry, Biology, a humanity plus Core Maths are examples of possible combinations.
My children did various combinations of Maths, a physical science and a humanity or social science (inc NEA). They also did FM with options in stats that would have supported CS routes even though CS was not taken. The mix worked for them and kept a lot of pathways open.