Unfortunately not, Lynn. The lime will not come out of suspension by just leaving it sitting. If you have a rainwater butt this water is slightly acid and suitable for acid loving plants. Many homes in your area will have a water purifier/softener/de-ioniser in the kitchen to feed the washing machine and kitchen tap. This water should also be suitable.
Just thinking aloud - when you boil the kettle you will get a heavy lime scale inside it; I don't know if boiled and cooled water would be suitable or not?

Yes, it will be, Bulbaholic, that's what I was about to suggest. Boil it, cool it and use it. Also water from a condensing tumble drier is lime free...

Many thanks for replying. Have to descale the kettle on a regular basis! Will have to do it even more now that I'll be using it for watering! Lynne

I fill a large old dustbin with tapwater, then add a little vinegar (advice thanks to a neighbour) and leave to stand for a few days, before using it to water my acid-lovers. Boiling water is a very expensive exercise, and I was taught that since it removes all the dissolved oxygen, it wasn't particularly good for plants anyway. Any comments, anyone?

Sorry keep putting my thanks in the wrong place.Does it have to be brown or white vinegar Gattina. Will try to find a marble Andrew. Very helpful tips.Thank you all.

To be honest, I doubt the vinegar color matters, Lynne. We can't buy malted vinegar here, so I used the cheapest and slightly "gone off" vinegar in my cupboard! Don't put too much in!

I'll be honest and say I never, ever bother to boil water for my acid lovers - if there's no rain water, tough, they'll just have to put up with tap water and be grateful for any water they're getting, life's far too short to be faffing about preparing water specially for fussy plants. No noticeable deleterious effects on the plants, and in the last 2 years, all have been watered with mains water due to the dearth of rainfall here.They are, though, in ericaceous compost, and some of them get treated with sequestrene if necessary. The only side effect is you get a layer of limescale round the pot on the inside at the top, well, in plastic pots anyway.