At my DC’s school half the students are allocated to French and half to Spanish in Y7. They later get the choice to pick up the other one too.
About 10% take the opportunity, which does seem quite low - but those that opt not to instead get the chance of introductory courses in business, media, photography or law, which do seem quite a bit more vocational.
There is the option to do both for GCSE, which again, is a small minority of keen linguists.
At A level, the classes are small, but particularly high-achieving. I think quite similar to the further maths A level it’s pretty self-selecting, you only choose it because you have natural ability and it’s your passion.
There is still the option of AS level and that’s a bit more popular.
You can choose both French and Spanish but I think that’s pretty unusual, one or two persons per year territory.
I do think studying two helps to reinforce both, tbh I think that’s one of the big issues. Most students only get the chance to try out one, and it’s a lot easier to realise you might like, or be good at, learning languages when you get to try more than one.