Thanks all. Joe90, thanks for the link. Yes, I definitely wouldn’t say it would be classed as a permanent residence!
Even if I put a settee and TV in there, it would never have a kitchen, bathroom or bedroom...
I just wasn’t sure of splitting the garage with a stud wall and insulating the office part of there were then regulations because of fire risk or something else from the remaining garage, although I suppose there has to be common sense limits, as it’s only a small space I guess, but difficult to find a 100% definitive answer, although logically it makes sense that it shouldn’t as no one would ever live in there ... just didn’t want issues when selling if I said there was an office detached from the house as part of a conversion that’s all