JMH Living as you do here in the UK and purchasing Lab grade distilled water. I hope you don't mind me saying it is a little like taking "Coal to Newcastle" the sky does all the distillation for you, just collect rainwater it is extremely cheap and we do have a lot falling on this island. Just strain it through a clean cloth and failing that the water from a home de humidifier I can also recommend to. I have used nothing else for many years.

The only lessons in my life I truly did learn from where the ones I paid for!