It's very odd. Don't get rid of it out of hand, it might be a rare butterfly or moth. Will try to find it online. I would be inclined to wait and see what it is. Interesting.

Fascinating....I would like to know what it is too.

I found this...

Quick facts
Common name Fluted scale
Scientific name Icerya purchasi
Plants affected Citrus, Acacia, Choisya and many other mainly woody plants
Main cause A sap-sucking insect
Timing Present all year round

The adults are flat, oval insects, 4-5mm long and reddish brown in colour. The females are perched on the edge of white waxy mounds in which eggs are deposited. These egg mounds have a distinctive grooved or fluted appearance. The young nymphs are oval and brownish but have a white waxy coating. Adults and nymphs can be found together all year round on the stems and foliage. Frequent host plants are Citrus, Acacia and Choisya but it can also attack many other woody plants.

Fluted scale sucks sap from a wide range of trees and shrubs. Heavily infested plants lack vigour and can be killed. A black sooty mould may grow on the insect's sugary excrement.

Is it a new plant? If so you should warn the supplier as they may have an infestation. One of the new(ish) wave of alien species taking advantage of climate change.

Well done for finding it. How unusual. Is that its egg sac?

Thank You for finding out what bug it is Michaella, wish you had been wrong and it had of been a rare butterfly or moth, now I'm going to have my work cut out for me trying to get rid of it all, it attacks Choisya's too, we have a big Sundance hope that hasn't got it. :o((
What a big egg sack it is too :-O
Ha! Not looking forward to squishing them :O(

Chemical control

Plants that are small enough to be sprayed can be treated with deltamethrin (e.g. Bayer Sprayday Greenfly Killer), lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), thiacloprid (e.g. Bayer Provado Ultimate Bug Killer) or acetamiprid (e.g. Bug Clear Ultra). On citrus plants where the fruits are going to be eaten, only organic insecticides, such as plant oils (e.g. Vitax Organic 2 in 1 Pest & Disease Control, Bug Clear for Fruit & Veg) can be used. Several thorough applications will be needed with plant oils to control the nymphs as they hatch.

In many parts of the world, an Australian ladybird known as the vedalia ladybird, Rodolia cardinalis, has been released as a biological control for fluted scale. This ladybird is not commercially available in the UK but it has been found in some London gardens. It probably arrived accidentally, along with the scale insect, on imported plants.

found the above on Google, I do not like using chemicals but sounds like this needs a good one, darned pests, I have dreadful problem with lily beetle do not need this hope the information helps. :O)

quit an amazing structure I think .

Taken them all off now and flushed um down the drain, hopefully the stuff in the drains will kill um LOL, I will be keeping a check on the stem & branches to see if there are any I mist :O))
Yes! Noseypotter. The structure is quite amazing, seemed a shame to destroy them :O(