For researching earlier hymns ("All hymns printed anywhere in the world with English-language texts up to 1820, and their publication history up to that date"), The Hymn Tune Index: A Census of English-Language Hymn Tunes in Printed Sources from 1535 to 1820, 4-Volume Set, edited by NICHOLAS TEMPERLEY (Clarendon Press Oxford, 1998) is greatly helpful, though this is an index and contained no texts. The price is $550.00, but mercifully the Index itsef can be used online too (CLICK HERE).

~Masato