Hey, I live in the UK, and still take you seriously. There is nothing youc an do if England is a developing country. Chill
In the UK you might want to try Maidenhead Aquatics, they have stores all over and do RO for £7 per 25litres. Halfords does distilled water too, but its more expensive. That said, given the costs, its much more "efficient" to buy a RO unit.
Additives will bind with heavy metals in your water. Problem is, thats precisely where they will stay, in your tank. The chemicals bind with the heavy metals and (depending from what chemical/metal is beidn bound) they will either precipitate in solid form, and react to form a different material (usually an oxidisation of the metal). Though this will render them fairly harmless, more sensitive corals, shrimps and invertebrates will NOT like it.
A second problem is provided by the other things present in British water. What you want to add to your tank is H20+Salt+Minerals (in a controlled fashion). British water has ludicrous amounts of minerals (thats why its so hard that people around London call it Liquid Rock). From Thamves Valley Water:
Soft water particularly reacts with the lead pipe work, hard water such as that supplied in the Thames regions does not readily dissolve lead from the pipe work, hence levels are low and exceedences of the standard are very rare.
As the water pipes are so old in most of England (it used to be a fully developed and industrialised country once upon a time... remember?) and haven't been replaced; water companies found out that the lead was wearing off into the drinking water of their clients. Poisoned clients end up dead or dying, and as such can't pay their bills. Thats not a good thing, now is it? Solution? change the pipes? No way, too expensive. Just add a brew of chemicals that will readily bond to the lead pipes, thus coating them with a sulphate (or carbonate, depends on what is added). What happens to the chemicals that don't bond? Well, they will end up in your tank (and your stomach if you trust tap water in England). These chemicals are NOT metals (heavy or otherwise), and as such, wont be affected by additives...
Some places will even deliver the water to your door... How much easier can it get? Alternatively, if you need materials to convince your mother to get an RO unit, simply put a large pan of water on the stove. Place a glass pane (or plate) a few cm's over the top at an angle, and a cup/bowl on the side. The water will evaporate, condense on the glass/plate and drip into the bowl. Do this once or twice, and all of a sudden RO is a better idea.
One VERY important rule about fishkeeping though. Relax
This is a relaxing hobby, don't flame people trying to give advice, or you wont get ANY advice. Lynden, have a hug ({); remember, yust because he thinks youre from the US doesn't mean he understands the difference between USA and Canada... Betta5... don't EVER compare a Canadian to an American from USA. Its like saying Irish, Welsh, Scottish are all English...
Michele