A couple of points about this.
- English reports (KF53 E6; also available online via the catalogue) are usually a good source of early English case law but they don't have everything.
- Dictionaries of legal citations and abbreviations are beautiful things. And include references to books as well as primary sources. I used the Raistrick book (on the reference shelves at K112 R433) but the online Cardiff index would have solved this too.
- The library catalogue is also a beautiful thing, even for very old material.
- And one more thing - the Eltham v Warreyn case is cited in a number of ways - sometimes just like that, sometimes it's the Inhabitants of Eltham or the Parish of Eltham, sometimes with a date, sometimes without. So be a little flexible with your search techniques in case you miss what's there.