You could try crushing up rhubarb leaves' leave them in a bucket of water,the oxalic acid from the leaves will change the 'lime' into calcium oxalate, which is practicaly insoluable and which will evenully settle out.

I wouldn't panic about the raspberries, they are fine in mildly alkaline conditions. In the short term, your soil pH (potted?) is more important than the water you use. Rainwater is perfect for longterm use. Presumably, most of the water they receive will be rainwater anyway unless they are potted.

Blueberries are more picky and you will probably need to amend garden soil, or use ericaceous compost in a container.

Thank you! Now I just need to grow some rhubarb... or find someone who does...
I've planted the raspberries & blueberry in the ground, but dug in a lot of ericaceous compost and manure first. I didn't actually test the soil pH afterwards.
So far, we've had enough rain to keep them thoroughly watered.

You could try mixing some cider vinegar with the tap water. In the meantime, put out a few buckets...I'm sure it'll rain soon! Not pretty, but it'll collect the water until you can get a water butt.

Alcina

Thanks again! What proportion vinegar to water?

Dilute standard household vinegar about twenty times to get the pH around 4, assuming you started with water. This would be one cup per gallon of water. Rainwater will have a pH around 5, which is good for blueberries. You could still add vinegare but make sure to dilute it at least twenty times so that it doesn't become too acidic.

Hard water might still be alkaline after this treatment, the only way to be sure is to test your water. If you don't fancy this idea, use distilled water until you can get some rainwater. Some, maybe all, Surrey water is very hard and I wouldn't use it at all on blueberries.

I just read my reply and it even confused me! A couple of typos don't help. Keep it simple!

Dilute household vinegar with twenty parts of soft water for acid-loving plants. Don't use very hard water for any length of time, even with added vinegar or another acid.

Thank you, shrubs'n'bulbs - I'll try filter jug water with added vinegar if the dry season kicks in before I get the water butt.