I want to stress that I'm not intending on driving in Seoul, but rather pick up a car once I'm leaving the city or elsewhere in the country if necessary.

I think from all your responses, what I will do is to wait until I get there to see how public transport will work out for me. At the moment I don't feel too worried about getting lost due to the language problems (which I thought would also be present when trying to get a bus or train as well) but this could be completely different on the ground so to say.
I expect I'll head to my first destination outside of Seoul and if I feel like I'm not exploring as much as I hoped, then I'll book a car on the internet as I would at home.

I'll look into booking a USO DMZ tour as soon as possible too.

I will report back as to how I get/got on.

Thank you all again!