I pay council tax of 120/month. 400 a month is far too high for 2 people - according to the ons [0] the average for a family of 4 is 56.80 (which seems a little on the low side to me, but is definitely enough for 2 people) - we spend a little less than that on breakfast/lunch/ 7 days, and dinner 6 nights for 2, and that includes our non food shopping expenses (e.g. toiletries, cleaning products).
Not to mention, if you're feeding two people, then the second person in the house presumably has an income. Presuming a pension, that now means your income is 1280/month. Remember that you get free travel, discount on heating (which reduces your £100/month bills)
Based on your comments in this thread, I can only assume that you like to indulge, and part of that indulgence is in price (seriously, 400 quid a month is exorbitant for 2 people), and that's perfectly fine. What's not ok is projecting your inability to live without sirloin steak, fresh fish, imported cheese on to everyone. You come across like an elitist snob.