Heard over the grapevine something that I have long practised - it is nice to know it also occurs in the birthplace of mass-use of mobile phones - Finland. Texting not calling.
I tend to text people if I know I might interrupt them, or they may be busy, like at work. It allows the receiver to prioritise without shame or affront. It is considerate.
In Finland, I hear, this is a common dimension to mobile phone etiquette. I hope it spreads to the UK.