"In the Bleak Midwinter" is a 19th century carol, written by Christina Rossetti (she of the Pre-Raphaelites) with the tune "Cranham" by Gustav Holst.

If you can get hold of them, the two cds by Maddy Prior and the Carnival Band, "Tapestry of Carols" and "Carols and Capers", are good source, as is their other album of Gallery Hymns: "Sing Lustily and With Good Voice". There's a broad spread of periods, but there are sufficient notes to go with them.

As previously mentioned, the Oxford Book of Carols is excellent. It also gives some quite useful history on a number of the carols. Also, where a more modern version is being used, it often gives the original in the footnotes.

Andrea