The sediment filters that David mentions are simple to install in line on your main input pipe.  If it's black Alkathene, just cut the pipe and connect the filter.
For cooking we use the 5 or 8 litre bottles (supermarket own brand) and for drinking, Bezoya (high quality spring water) available in 1.5 litre or 5 litre bottles.  Although you might not be used to buying drinking and cooking water, it's a lot cheaper than paying water rates in UK. :-)