I do not have direct experience with OC&C, however from what I have heard the standard process involves at least two rounds, with two cases in each of them and fit questions at the beginning. The cases are pretty similar to the standard ones in consulting, and usually involve market sizing.
Below you can find some examples of OC&C cases I found online referring to interviews in UK:
- Our company could go online but analysis of competitors shows we lag behind in total shop area. What should we prioritise?
- How many steps did you take to get here?
- A client has experience a surge in demand for their product, walk me through your analysis.
- What is the size of the UK market for water machines?
- What would a UK-based alcoholic beverage manufacturer have to consider in order to try to expand its market share?
- What is the size of the UK biscuit market?
- Estimate the market size for water coolers in the UK.
- Estimate the market size for computer hardware for businesses in the UK.
- How many vet practices are there in the UK?
- What is the size of the UK gift card industry?
For new graduates, they may also require a numerical and verbal test (usually SHL) and an online case study at the beginning of the process.
Hope this helps,