Do you live near a good Oriental grocery? Better yet, near SE London? A well stocked store will expand the things you can cook for your guest, and SE London is home to Koreatown and an enormous H Mart.
A homesick Korean will miss a good bowel of rice, kimchee, banchan, and a good soup.
Most modern Koreans make their rice in a pressurised cooker but I doubt that your guest will require that level of preparation - a decent bowel of short grain rice will do.
Kimchee is a must - have several varieties. Mat kimchee is the typical nappa cabbage one, and other varieties can easily be found (cucumber and radish are the other most common).
Banchan are small bowels of sides to serve along with the rice. Steamed and sauteed bean sprouts with sesame oil, sesame seeds, and spring onions. Spinach prepared in the same way as the bean sprouts - a variation which I grew up with is sauteed watercress prepared this way. Firm tofu sliced and pressed to remove excess water, pan fried, and seasoned. Sliced sauteed courgette is also easily prepared. Also commonly presented and easily prepared is thick seasoned omelette sliced into cubes. Loads of possibilities - the key is small amounts and several of them.
Grilled salted whole fish is very popular - particularly mackerel. My parents go mad for the mackerel in the UK each time they come.
A comforting soup, at least for my parents, is a must. These are usually seasoned with dried anchovies and daengang +/- gochoojang. There is often a bit of pork to add flavour. this web site is good for recipes. I have liked the stews page, but if you go to the home page, there are many more categories.
Now, if you live near the H Mart, you life will be made much easier as they sell pre-made banchan, stews, pre-marinated meat for grilling, and fish varieties Koreans love. It is as big as Costco, and the first place my Mom wants to go to in London.
Good Luck!