I agree with albalass,
The Highland Spring will be water from a natural spring,with carbon dioxide added.
The Somerfield (value and ordinary) will be basically carbonated tap water,hence the difference in price.
I buy Badoit or Perrier,or sometimes Evian.These are Mineral Waters,that is water that has percolated through rock.These three are also some of the very few that are naturally carbonated,that is they bubble to the surface containing natural carbon dioxide.
They are expensive,but as Rollo says,you pays your money,and makes your choice.