I'd like to kibbitz on this one. All that I'm seeing is a bunch of spider webs with flower debris and old leaves caught in them, but you shouldn't take my assessment seriously. The people familiar with the UK will almost certainly know better than me.

Spiders webs are nothing to worry about but i did wonder about the brown leaves near the bottom - just hoping it isn't the beginnings of box blight?

Box caterpillar moth is the culprit. Slide some plastic sheeting under the shrub and give it a good shake. Brake up as much of the webbing as possible. Give it a good spray with a systemic insecticide. Next year perhaps give the shrubs a spray several weeks earlier as a preventative. A couple of day's ago, I noticed that I have the same problem on my Buxus for the first time. Give them a good feed to bring them back to good health.

Agree with Jimmy - we had it on ours last year, haven't checked this year.