Scale insect alright, there's a large amount of it about this year, it's everywhere. Scrub off if you can bear to, and its' alright to use soapy water, though best with horticultural soap or eco friendly washing up liquid - the advice about soapy water and bays is to prevent people from using it as a spray on the leaves for aphids, so the bark will be fine. Most people don't realise how toxic washing up liquid and water is as a mix, unless its eco friendly - in some cases, worse than an insecticide.

I believe that by the time you see the white fluffy bits the scale insect has gone anyway.

No - scale insect creates the shield and, once attached, remains immobile for most of its life. Eggs are laid beneath the scale insect's body, and when the nymphs hatch, they come out and crawl around, then fasten on, form a scale and repeat the process. Except for cushion scale - they lay eggs in white, waxy fibres.

Thank you, scrubbed and was environmentally friendly Bamboo! Mentally though I haven't stopped itching yet.. There's something about being up in a tree full of insects, even ones that don't move... yuk!

These are pretty yucky too - I had to do the same thing last week on an Acer, which fortunately was only 4 feet tall, but not a pleasant task.