Hi maangchi and all your fans, my name is Cristina, currently living in london. I am a big fan of maangchi's korean cooking :) I love trying different kind of foods, and korean food is one of them. So here are 2 of korean groceries in the UK, london.
There is one called Seoul Plaza 4, located at
136 Golders Green Road,London,NW11 8HB,Tel 020 8731 7999,Tube Golders Green.
Also one called Hanna Supermarket
41 Store Street, London, WC1E 7DB,Tel 020 7636 4118,Tube Tottenham Court Road,Goodge Street
( I went to this shop today to get ingredients for making kimchi and spicy rice cake, surprisingly prices are quite expensive, the one in golders green is so much cheaper, i think because hanna supermarket is located more towards city and thats why its more expensive. So i got most of my ingredients and i will try to make kimchi this weekend.
Hope this info will help you maangchi and all your fan :)