Anvis systems are really no different to other in service NVD. While it is true step in Visors are common place they aren’t fielded for the Mk 10 RW helmet and the RVC has a unique Fireplace mount to accept inserts for different NVD types
In answer to your question though most guys wear no protection or use one of the cleared dust/ballistic/ snow goggles. Some use goggles that aren’t quite so cleared.
Due to the NVD fireplace mount fittings on Mk 10 RW unfortunately you cannot employ the clear visor with NVD fitted unlike the standard alpha mount which is excellent.
The French DGA have an FR tested Alpha helmet which is excellent and is a 928 variant including face shield and Powered NVD installation. But in all the burns footage I’ve seen the UK Helmets haven’t been a specific concern! So not something to be overly concerned about.
FR AEA as a whole has come on leaps and bounds and our crews are now the best protected they have ever been by quite some margin.