This is very impressive and difficult to maintain in London. Rent for a "double" room - meaning a room in a flat/apartment or house that fits a US full or European double bed is like 900/month right now. Spending only 1200/month is very difficult to achieve. I have no idea how this is feasible. To add to rent, local stores are usually more expensive than the supermarkets.
Maybe you ought to make a masterclass on this topic.