List entries attributed to category parent or category children *only*

Hi - I posted something about this in the Tech Support forum but I think that’s the wrong place for it. I’m working on something that has two-level categories (parent & child) and depending on the page, I want to display either entries related to parent-level only or child-level only, but not both together.

The categories look something like this:

Scotland Northern Ireland Wales England - London - South West … etc

So on one page I want to list entries attributed to Scotland, NI, Wales, England only (not any of the sub-regions) and on another page I just want to list entries categorised as sub-region only. I’ve tried lots of different ways of doing this with standard tags but am coming to the conclusion that I might need to use the query module to do this - am I wrong? (I hope so because I’m useless at writing sql queries!) Is there a way of handling this with the channel:entries and categories tag and an embed (bearing in mind that an entry tagged as ‘South West’ would also ca categorised as ‘England’)?

I don’t think this should be that complicated… is it?