Food to me is quite compartmentalized: Eating in at home, Eating out routinely (fast food, hawker food), Eating out at restaurants for occasions and really atas (high class) restaurants reserved for the very special occasion.

Eating in at home/Cooking for lunch is cheaper in the UK. Eating out routinely is more expensive and restaurant wise, the prices are thereabouts.

Why the disparity? First I have to qualify that with the UK's rate of VAT. VAT is just like our GST levied at the point of sale. Unfortunately, it is 20% and not 7% like in Singapore. Quite high huh!
VAT is levied on food sold for immediate consumption (e.g. in a restaurant) but is NOT levied on essential items. This includes stuff like medical prescriptions (7.85pounds per prescription regardless of quantity or type of medicine), food and drink for human consumption (excluding stuff like alcohol, fizzy drinks, sweets, ......