Are you looking for authentic polyphony for the Mass in English and you feel you have resorted to Tallis's If Ye Love Me once too often? If so, then you should investigate the scores available at EnglishMotets.com. 

This is a project created by Heath Morber who has adapted music by de Victoria, di Lasso, Palestrina to English translations of motets and liturgical texts including the Ordinary of the Mass. The complexity and difficulty of the arrangments vary so that there are some suitable for beginners and some for more experienced singers. There are arrangements are for two, three and four parts. 

When he started this project, Heath had in mind Catholic musicians who wanted to expose their congregations to the beauty of Renaissance polyphony and think that the vernacular may be a safe way to introduce this music to people in the pews who may balk at pieces in Latin. 

He already has already made over 200 pieces available and is adding more month by month. At the moment he is asking for a one-time payment of just $30 in exchange for access to the full and expanding library of titles as long the site and the internet exists. 

Here are two samples from the site. First, Answer My Prayer, an STB three-part arrangement of Exaudi Me Domine by Orlando di Lasso:

Second is Whoever Follows Me, a two-part (TB or SA) arrangement of Qui Sequitur Me also by Orlando di Lasso:

For more details, go to EnglishMotets.com.