Thanks, and interestingly I bought not only a hand-held reamer today but also a step drill bit! I'm aiming to use the former but will have the latter on standby.
I love the fact that whatever job you need to do, someone has invented a tool. However, there is one major problem - knowing what that tool is called! I'd never heard of a step drill until I searched reamer and they appeared low in the results 🤔
This is the body in question, I'm hoping next time I post a photo it looks a whole lot better