I've got one of those also. The guys over at
http://britishmilitariaforums.yuku.com/

really like those old Martini's and they'll get you up to spped quickly.
I Hollis was the retailer, not the maker. They put their stamps on guns of the trade. They are generally a lower grade of rifle but not always. Your's looks pretty good. How's the bore? Have you slugged the barrel yet?