There was a great deal of excitement when the Crosby Garrett Helmet was found in Cumbria last year then sold at Christie's (below, see catalogue), so I thought it might be worth pointing out several similar mask helmets found in Britain.
The Newstead Helmet, now in the National Museums of Scotland is in much poorer condition but is interesting as it was found near Melrose in Roxburghshire, Scotland. The provenance was the Roman fort at Trimontium along with the face mask from a second helmet, and a very elaborate helmet without a mask, and assorted other pieces of military equipment. The Newstead Helmet is interesting as bits of wool remained, showing it had once been lined. The main helmets can be seen here.