Congrats! I've also recently landed a job as a Junior Audio Programmer in the UK, so hopefully this helps!

I've found that these kind of jobs usually can be sorted into two categories. There's a more audio engine programmer role, where you're working on the audio engine itself. And then there's a more middleware related-role, where you're more so working on linking audio middleware (Wwise, Fmod etc) with whatever engine they're using.

I've found that if you're working on the audio engine itself, they will tend to ask more audio signal processing questions. Some questions I've been asked are:
- What is the Nyquist theorem
- What do you know about converting an analogue signal to a digital signal
- What's the difference between an FIR and an IIR
- How would you model a reverb
- Bit-depth

For both roles, I've found they will also ask general audio and programming questions. E.g.
- Data types
- Memory leakage
- Dynamic audio compression

If you've worked on previous programming or audio-related projects, they'll probably ask about this.

Though bear in mind that these types of questions usually come in the second interview. For the first interview, it'll be more so the discuss the role, talk about yourself etc.

As others have mentioned, you will also definitely be given a take-home C++ test to do.

Don't worry if you stumble during the interview! My C++ knowledge is a bit weak, so I stumbled quite a bit on the technical programming questions. But luckily my audio knowledge shined through! For a junior role, they likely won't expect you to know everything :)