How do I bathroom / kitchen / extension? etc.

We’ve got an EcoWater one. Can’t say anything about it other than it does exactly what is supposed to do.

We’ve got one with a carbon filter too, which helps with taste.

Would recommend. We’re in a really hard water area and everything from showers to washed clothes are nicer.

we just got a harvey, so far so good

I went through the Harvey's spiel. Didn't get one in the end for a few reasons. Cost obviously but also didn't want to lose the cupboard space and didn't want to replace the kitchen sink tap or add a drinking water tap.