If you cant find buttermilk then this is great for you, if you can then use it and don't add the lemon.
Pour the milk into a jug and add the lemon juice.
Leave to stand for 5 minutes for it to turn into buttermilk
While this is happening weigh out your other ingredients
Put the flour, bicarbonate of soda and the salt in a large mixing bowl
Pour in the buttermilk and combine together into a large ball
Don't overwork but just form into the ball
Place on a lined and floured baking tray
Cook for 35-40 minutes on 180oc for a fan oven
Test by putting in a wooden cocktail stick and if it comes out clear then it's done. Also tap on the bottom of the loaf and if it sounds hollow then that is a great sign