Mike, I’m in the US and here we would look in our phone book yellow pages under the heading Water Conditioning, treatment, filtration etc. and call a water treatment guy/gal. Another is the heading Water Analysis or Water Testing Labs.
Re-reading your initial post I see you say when the water sits it has the taste, what about fresh out of the spigot? If not, then I’d guess oxidation of iron, manganese etc. might be happening in the glass and that could be the cause of the metallic taste. Have you sanitized any water container you use in the ‘fridge to store your water in to chill it? Clean it first with a brush etc. and try some non-scented bleach and fill the container, then let it sit for about 30 minutes, then rinse well and see if that helps.
Gary
Quality Water Associates