in differernt partsof britaint .how do the person call their meals
Most people call them "breakfast", "lunch", and "dinner".
Some people call the ordinary evening meal "supper", and reserve "dinner" for more formal occasions; this usage was once associated with people of higher social status, but is now merely associated with people who want to give an impression of higher social status.
Some people call the evening meal "tea", and the midday meal "dinner". In this usage, the terms do not reflect how substantial the meal is. It's now associated with people of lower social status by the people who want to give an impression of higher social status.
(As you may have guessed, it's wiser on the whole to avoid naming your meals, in the UK.)