gary_rip:
Spring water is tap water...
That used to be true, but due to labelling regulations introduced a few years ago they are no longer allowed to treat tap water and call it 'spring water'.
Spring water is collected directly from the spring where it arises from the ground and must be bottled at the source. UK sources of spring water must meet certain hygiene standards, but may be treated in order that they meet limits set on pollution.
Mineral water emerges from under the ground, then flows over rocks before it's collected, resulting in a higher content of various minerals. Unlike spring water, it can't be treated except to remove grit and dirt. Different brands of spring and mineral waters will have differing amounts of minerals depending on their source.
That being said, I still wouldn't waste my money on any bottled water, there's no proven health benefits.