Read Steve's guide.
My tap water makes great dark beers. Pales are a challenge.
Could never justify all that empty plastic just to make my beer taste better though..
If your brewing kits it won't matter as water straight from the tap is ok providing it's good enough to drink whereas partial and all grain would be a different result.
Ok thanks guys im in norfolk and the water is hard as hell the kettle scales in days after descale i have access to ro water at work so could fill up there if needed but if its gonna make no diffrents to a kit beer then there no point