I can easily find floating row cover here in the US, but it has been a challenge to find UV treated insect netting.
What seems to be good quality and easy to find for floating row cover is Agribon (coming in several thicknesses). As I search for insect netting, it seems to be harder to find. The only thing I have found so far is a product called Proteknet “Biothrips” insect barrier.
https://www.johnnyseeds.com/tools-supplies/row-covers-and-accessories/row-cover/proteknet-%22biothrips%22-6.9-x-328-insect-barrier-7230.html
This seems to be overkill with it being 0.35 mm. I am looking to protect from butterflies/moths and it seems as though folks have said 5mm is sufficient. I know you are out the UK Charles, so not sure if you have any advice, but maybe others on the forum have some sources to share.
For now, I am going to stick with Agribon floating row cover until I can find a good resource for 5mm netting.